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US20210407817A1 - Iodine-containing fluorocarbon and hydrofluorocarbon compounds for etching semiconductor structures - Google Patents

Iodine-containing fluorocarbon and hydrofluorocarbon compounds for etching semiconductor structures Download PDF

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US20210407817A1
US20210407817A1 US16/913,696 US202016913696A US2021407817A1 US 20210407817 A1 US20210407817 A1 US 20210407817A1 US 202016913696 A US202016913696 A US 202016913696A US 2021407817 A1 US2021407817 A1 US 2021407817A1
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layer
iodine
etching
silicon
sio
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US11798811B2 (en
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Fabrizio MARCHEGIANI
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American Air Liquide Inc
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American Air Liquide Inc
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Priority to US16/913,696 priority Critical patent/US11798811B2/en
Priority to TW110122322A priority patent/TW202204297A/en
Priority to EP21828321.6A priority patent/EP4189727A1/en
Priority to KR1020237001313A priority patent/KR20230019981A/en
Priority to PCT/US2021/038668 priority patent/WO2021262841A1/en
Priority to JP2022579111A priority patent/JP2023531687A/en
Priority to CN202180048256.8A priority patent/CN116134981A/en
Publication of US20210407817A1 publication Critical patent/US20210407817A1/en
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    • H01L21/3086—Chemical or electrical treatment, e.g. electrolytic etching using masks characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane characterised by the process involved to create the mask, e.g. lift-off masks, sidewalls, or to modify the mask, e.g. pre-treatment, post-treatment
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Definitions

  • etch gases include octafluorocyclobutane (cC 4 F 8 ), hexafluoro-1,3-butadiene (C 4 F 6 ), CF 4 , CH 2 F 2 , CH 3 F, and/or CHF 3 . It is well known that selectivity and polymer deposition rate increase as the ratio of C:F increases (i.e., C 4 F 6 >C 4 F 8 >CF 4 ). See, e.g., U.S. Pat. No. 6,387,287 to Hung et al.
  • inert gases like Ar, Kr, or Xe
  • Ar, Kr, or Xe are added to the plasma where they are ionized and accelerated to the wafer surface bombarding the surface and supporting the etching process. Because they are inert gases, they do not directly participate in the chemical reactions of the etching process.
  • etch chemistries may not be able to provide a feature, such as a hole or trench, having an aspect ratio higher than 20:1, which is necessary in the newer applications (e.g., 3D NAND), at least due to insufficient etch resistant polymer deposition on sidewalls during the plasma etching processes.
  • the sidewall —C x F y — polymers, wherein x ranges from 0.01 to 1 and y ranges from 0.01 to 4, may be susceptible to etching.
  • the etched patterns may not be vertical and the etch structures may show bowing, change in dimensions, pattern collapse and/or increased roughness.
  • Bowing may result from sidewall etching of the mask layer, which may often be an amorphous carbon (a-C) material.
  • the a-C materials may be etched by oxygen radicals in the plasma which may cause increased opening of the mask and result in bow-like, or angled/curved, etch structures.
  • Iodine-containing compounds have been used as etching gases and/or reduction of global warming potential (GWP).
  • GWP global warming potential
  • Chung U.S. Pat. No.
  • 9,460,935 discloses etching first and second etching layers under plasma generated using, among others, 1,1,2,2-tetrafluoro-1-iodo-ethane. See also Karecki et al., “Plasma etching of dielectric films with novel iodofluorocarbon chemistries: iodotrifluoroethylene and 1-iodoheptafluoropropane”, J. Vac. Sci. Technol. A 16, 755 (1998); JP2006/108484; and TWI343601. Iodine-containing etching compounds have been shown significant reductions in global warming emissions compared to perfluorocarbon compounds (see S. Karecki, L. Pruette, and R. Reif, J. Electrochem. Soc. 145, 4305 (1998))
  • etching today has not been limited to selectivity to the photoresist mask. It is equally important to get high selectivity among other materials such as a-C, SiN, p-Si, SiC or other forms of Si a C b O c H d N e materials (where a>0; b, c, d and e ⁇ 20).
  • iodine-containing etching compound introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and a patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula C n H x F y I z , wherein 4 ⁇ n ⁇ 10, 0 ⁇ x ⁇ 21, 0 ⁇ y ⁇ 21, and 1 ⁇ z ⁇ 4;
  • the disclosed methods may include one or more of the following aspects:
  • iodine-containing etching compound introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and the patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula C n H x F y I z , wherein 4 ⁇ n ⁇ 10, 0 ⁇ x ⁇ 21, 0 ⁇ y ⁇ 21, and 1 ⁇ z ⁇ 4; and
  • the disclosed methods may include one or more of the following aspects:
  • iodine-containing etching compound introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and the patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula C n H x F y I z , wherein 4 ⁇ n ⁇ 10, 0 ⁇ x ⁇ 21, 0 ⁇ y ⁇ 21, and 1 ⁇ z ⁇ 4;
  • room temperature in the text or in a claim means from approximately 20° C. to approximately 25° C.
  • ambient temperature refers to an environment temperature approximately 20° C. to approximately 25° C.
  • substrate refers to a material or materials on which a process is conducted.
  • the substrate may refer to a wafer having a material or materials on which a process is conducted.
  • the substrates may be any suitable wafer used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing.
  • the substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step.
  • the wafers may include silicon layers (e.g., crystalline, amorphous, porous, etc.), silicon containing layers (e.g., SiO 2 , SiN, SiON, SiC, SiCN, SiOCN, SiCOH, etc.), metal containing layers (e.g., copper, cobalt, ruthenium, tungsten, manganese, platinum, palladium, nickel, ruthenium, gold, etc.) or combinations thereof.
  • the substrate may be planar or patterned.
  • the substrate may be an organic patterned photoresist film.
  • the substrate may include layers of oxides which are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (for example, ZrO 2 based materials, HfO 2 based materials, TiO 2 based materials, rare earth oxide based materials, ternary oxide based materials, etc.) or nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes.
  • oxides which are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications
  • ZrO 2 based materials for example, HfO 2 based materials, TiO 2 based materials, rare earth oxide based materials, ternary oxide based materials, etc.
  • nitride-based films for example, TaN, TiN, NbN
  • pattern etch or “patterned etch” refers to etching a non-planar structure, such as a patterned mask layer on a stack of silicon-containing films.
  • etch means to use a plasma to remove material via ion bombardment, remote plasma, or chemical vapor reaction between the etching gas and substrate and refers to an isotropic etching process and/or an anisotropic etching process.
  • the isotropic etch process involves a chemical reaction between the etching compound and the substrate resulting in part of material on the substrate being removed. This type of etching process includes chemical dry etching, vapor phase chemical etching, thermal dry etching, or the like.
  • the isotropic etch process produces a lateral or horizontal etch profile in a substrate.
  • the isotropic etch process produces recesses or horizontal recesses on a sidewall of a pre-formed aperture in a substrate.
  • the anisotropic etch process involves a plasma etching process (i.e., a dry etch process) in which ion bombardment accelerates the chemical reaction in the vertical direction so that vertical sidewalls are formed along the edges of the masked features at right angles to the substrate (Manos and Flamm, Thermal etching an Introduction, Academic Press, Inc. 1989 pp. 12-13).
  • the plasma etching process produces a vertical etch profile in a substrate.
  • the plasma etching process produces vertical vias, apertures, trenches, channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the substrate.
  • mask refers to a layer that resists etching.
  • the mask layer may be located above the layer to be etched.
  • the mask layer also refers to a hardmask layer.
  • etch stop refers to a layer below the layer to be etched that protects layers underneath.
  • device channel refers to layers that are part of actual device and any damage to it will affect device performance.
  • the term “aspect ratio” refers to a ratio of the height of a trench (or via) to the width of the trench (or the diameter of the via).
  • selectivity means the ratio of the etch rate of one material to the etch rate of another material.
  • selective etch or “selectively etch” means to etch one material more than another material, or in other words to have a greater or less than 1:1 etch selectivity between two materials.
  • R groups independently selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group.
  • R groups may, but need not be identical to each other or to R 2 or to R 3 .
  • values of R groups are independent of each other when used in different formulas.
  • film and “layer” may be used interchangeably. It is understood that a film may correspond to, or related to a layer, and that the layer may refer to the film. Furthermore, one of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may range from as large as the entire wafer to as small as a trench or a line.
  • etching compound and “etching gas” may be used interchangeably. It is understood that an etching compound may correspond to, or related to an etching gas, and that the etching gas may refer to the etching compound.
  • via is sometimes used interchangeably, and generally mean an opening in an interlayer insulator.
  • NAND refers to a “Negated AND” or “Not AND” gate
  • 2D refers to 2 dimensional gate structures on a planar substrate
  • 3D refers to 3 dimensional or vertical gate structures, wherein the gate structures are stacked in the vertical direction.
  • CAS unique CAS registry numbers assigned by the Chemical Abstract Service are provided to help better identify the molecules disclosed.
  • the silicon-containing films such as silicon nitride and silicon oxide, are listed throughout the specification and claims without reference to their proper stoichiometry.
  • the silicon-containing films may include pure silicon (Si) layers, such as crystalline Si, poly-silicon (p-Si or polycrystalline Si), or amorphous silicon; silicon nitride (Si k N l ) layers; or silicon oxide (Si n O m ) layers; or mixtures thereof, wherein k, l, m, and n, inclusively range from 0.1 to 6.
  • silicon nitride is Si k N l , where k and l each range from 0.5 to 1.5.
  • silicon nitride is Si 3 N 4 .
  • silicon oxide is Si n O m , where n ranges from 0.5 to 1.5 and m ranges from 1.5 to 3.5. More preferably, silicon oxide is SiO 2 .
  • SiN and SiO in the following description are used to represent Si k N l and Si n O m containing layers, respectively.
  • the silicon-containing film could also be a silicon oxide based dielectric material such as organic based or silicon oxide based low-k dielectric materials such as the Black Diamond II or III material by Applied Materials, Inc. with a formula of SiOCH.
  • Silicon-containing film may also include Si a O b C c N d H e where a, b, c, d, e range from 0.1 to 6.
  • the silicon-containing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge.
  • Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
  • FIG. 1 a is a cross-sectional side view of exemplary layers in a 3D NAND stack
  • FIG. 1 b is a cross-sectional side view of the exemplary layers in the 3D NAND stack showing polymer deposited on a sidewall during etching of the 3D NAND stack;
  • FIG. 1 c is a cross-sectional side view of the exemplary layers in the 3D NAND stack showing particles generated during alternating SiO/SiN layer etching of a 3D NAND stack;
  • FIG. 1 d is a cross-sectional side view of the exemplary layers in the 3D NAND stack showing selective etching of SiN exposed on the sidewall in the 3D NAND stack;
  • FIG. 2 is a cross-sectional side view of exemplary layers of a DRAM stack
  • FIG. 3 a is a cross-sectional side view of exemplary layers showing photoresist pattern over SiO insulation layer surrounding typical transistor device region to produce a transistor structure;
  • FIG. 3 b is a cross-sectional side view of the exemplary layers of FIG. 3 a after etching the SiO insulation layer;
  • FIG. 4 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C 3 F 7 I, O 2 and Ar;
  • FIG. 5 is a graph demonstrating the electron impact ionization energy (eV) versus species concentration (Torr) of C 3 F 7 I;
  • FIG. 6 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C 4 F 9 I, O 2 and Ar;
  • FIG. 7 is 1-C 4 F 9 I depth profile on a-C substrate
  • FIG. 8 is 1-C 4 F 9 I depth profile on a-C(B) substrate
  • FIG. 9 is 1-C 4 F 9 I depth profile on a-C(W) substrate
  • FIG. 10 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with cC 4 F 8 ;
  • FIG. 11 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with C 4 F 6 .
  • the disclosed methods include the steps of i) introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a silicon-containing film on a substrate, wherein the iodine-containing etching compound has the formula C n H x F y I z , wherein 4 ⁇ n ⁇ 10, 0 ⁇ x ⁇ 21, 0 ⁇ y ⁇ 21, and 1 ⁇ z ⁇ 4; and ii) introducing an inert gas into the reaction chamber; and iii) activating a plasma to produce an activated iodine-containing etching compound capable of etching the silicon-containing film from the substrate.
  • the inert gas may be Ar, Kr, Xe, N 2 . He or Ne.
  • the iodide ion in the disclosed iodine-containing etching compounds dissociates from the compounds at low energies (eV) (i.e., ⁇ 20 eV).
  • eV low energies
  • the disclosed etching compounds may be used in dry plasma etch processes that produce less damage to the underlying substrates because they can be performed at lower plasma energies.
  • the disclosed iodine-containing etching compounds may be particularly suitable for low k etch processes in which damage is a particular concern because lower plasma energy may produce less damage to the porous low k material surrounding the etch site.
  • the low damage to low k material may be due to the reduced generation of UV photons and F radicals given by iodine-containing etching compounds.
  • the disclosed iodine-containing etching compounds may also prevent loss of the critical dimension and decrease low k surface roughness.
  • molecules with two iodine atoms may enhance these benefits, although at a loss of volatility due to the size of the iodine atoms.
  • Iodine (10.5 eV) has a lower ionization threshold than Fluorine (17.4 eV) and the inert gases: Ar (15.8 eV), Xe (12.1 eV), and Kr (14 eV). Iodine may therefore be more easily ionized by the plasma than fluorine and iodine-containing etching compound may increase the plasma density. Iodine, being a heavy element (with a mass of 127 amu), may also behave similarly to the inert gases (such as Kr, with 88 amu, and Xe, with 131 amu) in the plasma and accelerate towards the wafer.
  • the inert gases such as Kr, with 88 amu, and Xe, with 131 amu
  • Iodine ions being heavy may be accelerated toward the wafers by the voltage applied during the plasma etch process and penetrate deeply allowing to etch deep pattern structures with high aspect ratio.
  • Fluorine's ionization threshold serves to maintain it as a neutral species.
  • fluorine typically participates in the etching process via chemical reactions. Iodine exhibits less chemical reactivity than fluorine and is ionized and bombards the surface during the plasma etch process.
  • the bond energy for C—I is also less than the bond energy for C—F, thereby causing the C—I bond to more easily break in the plasma compared to C—F bonds.
  • iodine ions may easily be doped into a-C mask layer. Since iodine is a heavy element that makes it easier to implant and penetrate deeply in the mask layer than lighter elements.
  • the iodine containing etching compound have a low to negligible atmospheric lifetime making them good candidates to reduce the global warming potential caused by perfluorocarbon compounds.
  • the iodide ion dissociates from the disclosed etching compounds at low eVs (i.e., ⁇ 20 eV), referring to the Comparative Example below.
  • iodide ion implantation into the mask feature, such as the surface and/or the body/bulk is likely. This implantation may help to strengthen, minimize the damage, increase etch resistance of the mask feature and help it maintain its shape during the etching process.
  • the composition of the pattern mask is modified. Applicants believe that the iodine ions modify the surface and incorporate into the bulk of the pattern mask layer by increasing the crosslinking with the organic mask layer (such as amorphous carbon mask).
  • the density of the pattern mask layer increases, making the pattern mask layer stronger.
  • the strengthening effect and the etch resistance improvement due to the iodine ions have been proved by showing that the etching rate of the pattern mask layer is lower when etched by iodine-containing etching compound than when is etched by the traditional etching gases, such as cC 4 F 8 and C 4 F 6 .
  • the disclosed iodine-containing etching compounds have the formula C n H x F y I z , wherein 4 ⁇ n ⁇ 10, 0 ⁇ x ⁇ 21, 0 ⁇ y ⁇ 21, 1 ⁇ z ⁇ 4.
  • the disclosed iodine-containing etching compounds may not contain any hydrogen having the formula C n F y I z , wherein 4 ⁇ n ⁇ 10, 0 ⁇ y ⁇ 21, 1 ⁇ z ⁇ 4 and y+z ⁇ 2n+2.
  • Exemplary C 4 iodine-containing etching compounds without containing H include C 4 F 9 I, C 5 F 11 I, C 6 F 13 I, C 7 F 15 I, C 8 F 17 I, C 9 F 19 I, C 10 F 21 I, C 4 F 7 I, C 5 F 9 I, C 6 F 11 I, C 7 F 13 I, C 8 F 15 I, C 9 F 17 I, C 10 F 19 I, C 4 F 5 I, C 5 F 7 I, C 6 F 9 I, C 7 F 11 I, C 8 F 13 I, C 9 F 17 I, C 10 F 17 I, C 4 F 8 I 2 , C 5 F 10 I 2 , C 6 F 12 I 2 , C 7 F 14 I 2 , C 8 F 16 I 2 , C 9 F 18 I 2 , C 10 F 20 I 2 , C 4 F 6 I 2 , C 5 F 8 I 2 , C 6 F 10 I 2 , C 7 F 12 I 2 , C 8 F 14 I 2 , C 9 F 16 I 2 , C 10 F 18
  • Exemplary disclosed iodine-containing etching compounds without containing H having a general formula: C n F 2n+1 I, where 4 ⁇ n ⁇ 10, are listed in Table 2. These molecules are commercially available or may be synthesized by methods known in the art. Their structure formula, CAS numbers and boiling points are included in Table 2. The disclosed iodine-containing etching compounds without containing H having a general formula: C n F 2n+1 I, where 4 ⁇ n ⁇ 10, may also include their isomers.
  • the disclosed iodine-containing etching compounds are suitable for etching silicon-containing films that include a layer of silicon oxide (SiO), silicon nitride (SiN), pure silicon (Si) such as crystalline Si, poly-silicon (p-Si or polycrystalline Si), or amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON, Si a O b H c C d N e , where a>0; b, c, d and e ⁇ 0, or combinations thereof.
  • the silicon-containing film may also include alternating SiO and SiN (ONON) layers or SiO and p-Si (OPOP) layers.
  • the silicon-containing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge.
  • the etch rate of SiN may be enhanced while maintaining high selectivity to the mask layer when the disclosed iodine-containing etching compounds include H, but are not limited to.
  • Exemplary compounds include C 4 HF 8 I, C 5 HF 10 I, C 6 HF 12 I, C 7 HF 14 I, C 8 HF 16 I, C 9 HF 18 I, C 10 HF 20 I, C 4 HF 6 I, C 5 HF 8 I, C 6 HF 10 I, C 7 HF 12 I, C 8 HF 14 I, C 9 HF 16 I, C 10 HF 18 I, C 4 HF 4 I, C 5 HF 6 I, C 6 HF 8 I, C 7 HF 10 I, C 8 HF 12 I, C 9 HF 14 I, C 10 HF 16 I, C 4 HF 7 I 2 , C 5 HF 9 I 2 , C 6 HF 11 I 2 , C 7 HF 13 I 2 , C 8 HF 15 I 2 , C 9 HF 17 I 2 , C 10 HF 19 I 2 , C 4 HF 5 I 2 , C 5 HF 7 I 2 , C 6 HF 9 I 2 , C 7 HF 11 I 2 , C 8 HF
  • Exemplary compounds include C 4 H 2 F 7 I, C 5 H 2 F 9 I, C 6 H 2 F 11 I, C 7 H 2 F 13 I, C 8 H 2 F 15 I, C 9 H 2 F 17 I, C 10 H 2 F 19 I, C 4 H 2 F 5 I, C 5 H 2 F 7 I, C 6 H 2 F 9 I, C 7 H 2 F 11 I, C 8 H 2 F 13 I, C 9 H 2 F 15 I, C 10 H 2 F 17 I, C 4 H 2 F 6 I 2 , C 5 H 2 F 8 I 2 , C 6 H 2 F 10 I 2 , C 7 H 2 F 12 I 2 , C 8 H 2 F 14 I 2 , C 9 H 2 F 16 I 2 , C 10 H 2 F 11 I 2 , C 4 H 2 F 4 I 2 , C 5 H 2 F 6 I 2 , C 6 H 2 F 8 I 2 , C 7 H 2 F 10 I 2 , C 8 H 2 F 12 I 2 , C 9 H 2 F 14 I 2 , C 10 H 2 F 16 I 2
  • Exemplary compounds include C 4 H 3 F 6 I, C 5 H 3 F 8 I, C 6 H 3 F 10 I, C 7 H 3 F 12 I, C 8 H 3 F 14 I, C 9 H 3 F 16 I, C 10 H 3 F 16 I, C 4 H 3 F 4 I, C 5 H 3 F 6 , C 6 H 3 F 8 I, C 7 H 3 F 10 I, C 8 H 3 F 12 I, C 9 H 3 F 14 I, C 10 H 3 F 16 I, C 4 H 3 F 5 I 2 , C 5 H 3 F 7 I 2 , C 6 H 3 F 9 I 2 , C 7 H 3 F 11 I 2 , C 8 H 3 F 13 I 2 , C 9 HF 15 I 2 , C 10 H 3 F 17 I 2 , C 4 H 3 F 3 I 2 , C 5 H 3 F 5 I 2 , C 6 H 3 F 7 I 2 , C 7 H 3 F 9 I 2 , C 8 H 3 F 11 I 2 , C 9 H 3 F 13 I 2 , C 10 H 3 F 15 I 2
  • Exemplary compounds include C 4 HF 5 I, C 5 H 4 F 7 I, C 6 H 4 F 9 I, C 7 H 4 F 11 I, C 8 H 4 F 13 I, C 9 H 4 F 15 I, C 10 H 4 F 17 I, C 4 H 4 F 3 I, C 5 H 4 F 5 I, C 6 H 4 F 7 I, C 7 H 4 F 9 I, C 8 H 4 F 11 I, C 9 H 4 F 13 I, C 10 H 4 F 15 I, C 4 H 4 F 4 I 2 , C 5 H 4 F 6 I 2 , C 6 H 4 F 8 I 2 , C 7 H 4 F 10 I 2 , C 8 H 4 F 12 I 2 , C 9 H 4 F 14 I 2 , C 10 H 4 F 16 I 2 , C 4 H 4 F 2 I 2 , C 5 H 4 F 4 I 2 , C 6 H 4 F 6 I 2 , C 7 H 4 F 8 I 2 , C 8 H 4 F 10 I 2 , C 9 H 4 F 12 I 2 , C 10 H 4 F 14 I 2
  • the molecules having 4 or more than 4 carbon atoms may provide better etch rate and sidewall protection, e.g., straight profile, no bowing, no tapering, no twisting, no incomplete etch, no variation of critical dimension from top to bottom of the structure etched, during the etching process than less than 4 carbon molecules.
  • the molecules having 4 or more than 4 carbon atoms may also provide a straighter profile, without bowing, tapering, twisting and incomplete etch, or variation of critical dimension from top to bottom of the structure etched than less than 4 carbon molecules.
  • the carbon 24 molecules are preferred because Applicants believe they will produce thicker passivation layers.
  • the disclosed iodine-containing etching compounds may provide high selectivity to mask layers, photoresist, etch stop layers and device channel materials and no profile distortion in high aspect ratio structures (HAR), such as those having an aspect ratio ranging from 1:1 to 200:1 such as DRAM and 3D NAND structures.
  • HAR high aspect ratio structures
  • the disclosed iodine-containing etching compounds may also provide high selectivity to mask layers or silicon-containing film, such as those having an aspect ratio ranging from 1:1 to 200:1 in contact etch applications.
  • the disclosed iodine-containing etching compounds may provide infinite selectivity for wide process conditions of etching.
  • the selectivity refers to the etching rate ratio of two different layers.
  • the selectivity for SiO layer vs. a-C layer is the etch rate of the SiO divided by the etching rate of the a-C layer.
  • the disclosed iodine-containing etching compounds may provide improved selectivity between the silicon-containing films and mask materials, less damage to channel region, improved critical dimension uniformity and reduced profile distortion such as bowing, twisting, tapering, notching, under-cut, maintain the same critical dimension from top to bottom of the etch structure and arcing in pattern high aspect ratio structures.
  • the disclosed iodine-containing etching compounds may also etch through alternating layers of p-Si, SiO, and/or SiN, resulting in a vertical etch profile. (i.e., demonstrating selectivity ranging from 2:1 to 1:2 between the alternating layers).
  • the disclosed iodine-containing etching compound plasma etches the alternating SiO and SiN (ONON) layers having a selectivity between approximately 1:2 to approximately 2:1 with respect to the SiO layer versus SiN layer.
  • the disclosed iodine-containing etching compound plasma etches the alternating SiO and SiN (ONON) layers having a selectivity of approximately 1:1 with respect to the SiO layer versus SiN layer.
  • the disclosed iodine-containing etching compounds are provided at greater than 95% v/v purity, preferably at greater than 99.99% v/v purity, and more preferably at greater than 99.999% v/v purity.
  • the disclosed iodine-containing etching compounds contain less than 5% by volume trace gas impurities, with less than 150 ppm by volume of impurity gases, such as N 2 and/or H 2 O and/or CO 2 , contained in said trace gaseous impurities.
  • the water content in the plasma etching gas is less than 20 ppm by weight.
  • the purified product may be produced by distillation and/or passing the gas or liquid through a suitable adsorbent, such as a 4 ⁇ molecular sieve.
  • the disclosed iodine-containing etching compounds contain less than 10% v/v, preferably less than 1% v/v, more preferably less than 0.1% v/v, and even more preferably less than 0.01% v/v of any of its isomers, which may be purified by distillation of the gas or liquid to remove isomers and may provide better process repeatability.
  • the disclosed iodine-containing etching compounds may contain between 0.01% v/v and 99.99% v/v of its isomers, particularly when the isomer mixture provides improved process parameters or if isolation of the target isomer is too difficult or expensive.
  • the disclosed iodine-containing etching compounds may comprise between approximately 50% v/v and approximately 75% v/v 1-Iodononafluorobutane and between approximately 25% v/v and approximately 50% v/v 2-Iodononafluorobutane and between approximately 25% v/v and approximately 50% v/v Iodononafluoro-t-butane.
  • the mixture of isomers may also reduce the need for two or more gas lines to the reaction chamber.
  • Some of the disclosed iodine-containing etching compounds are gaseous at room temperature and atmospheric pressure.
  • the non-gaseous (i.e., liquid or solid) compounds their gas form may be produced by vaporizing the compounds through a conventional vaporization step, such as direct vaporization or by bubbling with inert gas (such as N 2 , Ar, He).
  • the non-gaseous compounds may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into a reactor.
  • the disclosed iodine-containing etching compounds are suitable for plasma etching semiconductor structures, such as, channel holes, gate trenches, staircase contacts, slits, capacitor holes, contact holes, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films.
  • the disclosed iodine-containing etching compounds are not only compatible with currently available mask materials but also compatible with the future generations of mask materials because the disclosed iodine-containing etching compounds induce little to no damage on the mask along with good profile of high aspect ratio structures. In other words, the disclosed iodine-containing etching compounds may produce vertical etched patterns having minimal to no bowing, pattern collapse, or roughness.
  • the disclosed iodine-containing etching compounds may deposit an etch-resistant polymer layer during etching to help reduce the direct impact of the oxygen and fluorine radicals during the etching process.
  • the disclosed iodine-containing etching compounds may also reduce damage to p-Si or crystalline Si channel structure during etching.
  • the disclosed iodine-containing etching compounds selectively etch the silicon-containing layers from a buried landing layer or material which is a metal layer located at the bottom of the structure to be etched in most applications.
  • the disclosed iodine-containing etching compounds do not etch metal landing layers.
  • the buried landing layer may be an etching stop layer or a diffusion barrier layer.
  • Materials of the metal landing layers may be a tungsten metal worldline in a 3D NAND structure and/or another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof and/or etch stop layers such as metals or metal oxides or nitrides layer such as AlO, WO, HfO, TiO, TaO, InO, CrO, RuO, CoO, MoO, ZrO, SnO TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN, ZrN, SnN or combination thereof etc.
  • another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof and/or etch stop layers such as metals or metal oxides or n
  • the disclosed iodine-containing etching compounds induce little to no damage to the material at bottom of the contact hole, staircase and slit (such as tungsten metal world line in a 3D NAND structure and/or other metals such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof etc.) and/or etch stop layers such as metals or metal oxides or nitrides layer (AlO, WO, HfO, TiO, TaO, InO, CrO, RuO, CoO, MoO, ZrO, SnO TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN, ZrN, SnN or combination thereof etc.).
  • a barrier layer can also be composed of a combination of the previously mentioned metals and metals oxide and nitride, such a barrier layer being Ti/TiN, Ti/TiN/Ti, TiZrN, Ta/TaN, TaN/Cu/TaN, TaN/Ru/TaN etc.
  • a barrier might also contained silicide (such as TiSiN, TaSiN, TiSi 2 , MnSiO, etc.), phosphide (such as CuWP, NiMoP, NiP etc.), carbide (such as TaC, TaCN, WCN etc.), boride (such as NiMoB, NiB etc.) or combination thereof.
  • the disclosed iodine-containing etching compounds are suitably volatile and stable during the etching process for delivery into the reactor/chamber.
  • Material compatibility tests are important to determine if any of the disclosed iodine-containing etching compounds will react with chamber materials and degrade the performance of the chamber with short term or long term use.
  • Key materials involved in parts of the chamber, valves, etc. include stainless steel, aluminum, nickel, PCTFE, PVDF, PTFE, PFA, PP, kalrez, viton and other metals and polymers. At times these materials are exposed to high temperatures, for example, higher than 20° C., and high pressures, for example, higher than 1 atm, which may enhance their degradation.
  • the metrology methods may include visual inspection, weight measurement, measuring nanometer scale changes in scanning electron microscopy (SEM), tensile strength, hardness, etc.
  • the disclosed iodine-containing etching compounds may be used to plasma etch silicon-containing films on a substrate.
  • the disclosed plasma etching method may be useful in the manufacture of semiconductor devices such as NAND or 3D NAND gates or Flash or DRAM memory or transistors such as fin-shaped field-effect transistor (FinFET), Gate All Around (GAA)-FET, Nanowire-FET, Nanosheet-FET, Forksheet-FET, Complementary FET (CFET), Bulk complementary metal-oxide-semiconductor (Bulk CMOS), MOSFET, fully depleted silicon-on-insulator (FD-SOI) structures.
  • FinFET FinFET
  • GAA Gate All Around
  • Nanowire-FET Nanowire-FET
  • Nanosheet-FET Nanosheet-FET
  • Forksheet-FET Forksheet-FET
  • CFET Complementary FET
  • Bulk CMOS Bulk complementary metal-oxide-semiconductor
  • MOSFET
  • the disclosed iodine-containing etching compounds may be used in other areas of applications, such as different front end of the line (FEOL) and back end of the line (BEOL) etch applications. Additionally, the disclosed iodine-containing etching compounds may also be used for etching Si in 3D through silicon via (TSV) etch applications for interconnecting memory to logic on a substrate and in MEMS applications.
  • FEOL front end of the line
  • BEOL back end of the line
  • TSV silicon via
  • the plasma etching method includes providing a reaction chamber having a substrate disposed therein.
  • the reaction chamber may be any enclosure or chamber within a device in which etching methods take place such as, and without limitation, reactive ion etching (RIE), capacitively coupled plasma (CCP) with single or multiple frequency RF sources, inductively coupled plasma (ICP), or microwave plasma reactors, or other types of etching systems capable of selectively removing a portion of the silicon-containing film or generating active species.
  • RIE reactive ion etching
  • CCP capacitively coupled plasma
  • ICP inductively coupled plasma
  • microwave plasma reactors or other types of etching systems capable of selectively removing a portion of the silicon-containing film or generating active species.
  • Suitable commercially available plasma reaction chambers include but are not limited to the Applied Materials magnetically enhanced reactive ion etcher sold under the trademark eMAXTM or the Lam Research Dual CCP reactive ion etcher dielectric etch product family sold under the trademark 2300® FlexTM.
  • the RF power in such may be pulsed to control plasma properties and thereby improving the etch performance (selectivity and damage) further.
  • the plasma-treated reactant may be produced outside of the reaction chamber.
  • the MKS Instruments' ASTRONi® reactive gas generator may be used to treat the reactant prior to passage into the reaction chamber.
  • the reactant O 2 Operated at 2.45 GHz, 7 kW plasma power, and a pressure ranging from approximately 0.5 Torr to approximately 10 Torr, the reactant O 2 may be decomposed into two 0 radicals.
  • the remote plasma may be generated with a power ranging from about 1 kW to about 10 kW, more preferably from about 2.5 kW to about 7.5 kW.
  • the reaction chamber may contain one or more than one substrate.
  • the reaction chamber may contain from 1 to 200 silicon wafers having from 25.4 mm to 450 mm diameters.
  • the substrates may be any suitable substrates used in semiconductor, photovoltaic, flat panel or LCD-TFT device manufacturing. Examples of suitable substrates include wafers, such as silicon, silica, glass, Ge, SiGe, GeSn, InGaAs, GaSb, InP, or GaAs wafers.
  • the wafer will have multiple films or layers on it from previous manufacturing steps, including silicon-containing films or layers. The layers may or may not be patterned.
  • suitable layers include without limitation silicon (such as amorphous silicon, p-Si, crystalline silicon, any of which may further be p-doped or n-doped with B, C, P, As, Ga, In, Sn, Sb, Bi and/or Ge), silica, silicon nitride, silicon oxide, silicon oxynitride, Si a O b H c C d N e , (wherein a>0; b, c, d, e ⁇ 0), Ge, SiGe, GeSn, InGaAs, GaSb, InP; mask layer materials such as amorphous carbon with or without dopants, antireflective coatings, photoresist materials, a metal oxide, such as AlO, TiO, HfO, ZrO, SnO, TaO etc.
  • silicon such as amorphous silicon, p-Si, crystalline silicon, any of which may further be p-doped or n-doped with B
  • a metal nitride layer such as AlN, ZrN, SnN, HfN, titanium nitride, tantalum nitride etc. or combinations thereof; etch stop layer materials such as silicon nitride, polysilicon, crystalline silicon, silicon carbide, SiON, SiCN or combinations thereof, device channel materials such crystalline silicon, epitaxial silicon, doped silicon, Si a O b H c C d N e , (wherein a>0; b, c, d, e ⁇ 0) or combinations thereof.
  • the silicon oxide layer may form a dielectric material, such as an organic based or silicon oxide based low-k dielectric material (e.g., a porous SiCOH film).
  • An exemplary low-k dielectric material is sold by Applied Materials under the trade name Black Diamond II or III. Additionally, layers comprising tungsten or noble metals (e.g. platinum, palladium, rhodium or gold) may be used. Furthermore, examples of the silicon-containing films may be Si a O b H c C d N e , (wherein a>0; b, c, d, e ⁇ 0). Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.
  • a substrate 100 may include a stack of multiple layers as shown in FIG. 1 a .
  • FIG. 1 a is a cross-sectional side view of exemplary layers in a 3D NAND stack to produce a 3D NAND gate.
  • a stack of seven alternative SiO/SiN (i.e., 104 a / 104 b ) layers 104 is located on top of a silicon wafer 102 (i.e., ONON or TCAT technology).
  • the wafer 102 may be a buried landing layer or material, such as tungsten metal worldline in a 3D NAND structure and/or another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof etc. and/or etch stop or diffusion barrier layers such as metals or metal oxides or nitrides layer (AlO, WO, HfO, TiO, TaO, InO, WO, CrO, RuO, CoO, MoO, TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN or combination thereof etc.).
  • tungsten metal worldline in a 3D NAND structure and/or another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination
  • a barrier layer can also be composed of a combination of the previously mentioned metals and metals oxide and nitride, such a barrier layer being Ti/TiN, Ti/TiN/Ti, TiZrN, Ta/TaN, TaN/Cu/TaN, TaN/Ru/TaN etc.
  • a barrier might also contained silicide (such as TiSiN, TaSiN, TiSi 2 . MnSiO, etc.), phosphide (such as CuWP, NiMoP, NiP etc.), carbide (such as TaC, TaCN, WCN etc.), boride (such as NiMoB, NiB etc.) or combination thereof.
  • a hardmask layer 106 is located on the top of the seven SiO/SiN layers 104 .
  • the hardmask layer 106 may be an amorphous carbon (a-C) hardmask layer with or without dopants.
  • the hardmask layer 106 may be a layer of CVD, PECVD, ALD, PEALD or spin on deposited (SOD) amorphous carbon or doped amorphous carbon, silicon-containing spin on mask, or carbon-containing spin on mask.
  • the hardmask layer 106 may contain C and H, as well as other elements, such as boron, nitrogen, sulfur, chlorine, fluorine or metals (Al, Zr, Ti, W, Y) etc., to improve etch resistance during SiO/SiN layer etch.
  • the hardmask layer 106 is a doped a-C layer, for example, a boron-doped a-C layer, a tungsten-doped a-C layer, etc.
  • An antireflective coating layer 108 is located on top of the hardmask layer 106 .
  • a patterned photoresist layer 110 is located on top of the antireflective coating layer 108 .
  • a SiON layer (not shown) may be present between the antireflective coating layer 108 and the hardmask layer 106 to transfer the pattern in photoresist layer 110 to the hardmask layer 106 to form a patterned hardmask layer.
  • a SiON layer (not shown) may be present between the antireflective coating layer 108 and the hardmask layer 106 to transfer the pattern in photoresist layer 110 to the hardmask layer 106 to form a patterned hardmask layer.
  • the number alternating SiO/SiN or SiO/p-Si layers 104 in the stack of the substrate 100 may vary (i.e., may include more or less than the seven SiO/SiN ( 104 a / 104 b ) layers depicted).
  • FIG. 1 b is a cross-sectional side view of the exemplary layers in the 3D NAND stack of FIG. 1 a showing polymer deposited on a sidewall by etching.
  • the disclosed iodine-containing etching compounds may produce fragments during the plasma process that are suitable for both anisotropically etching the silicon-containing films 104 and depositing an I-containing polymer passivation layer 212 on sidewalls of a structure being etched as shown in FIG. 1 b .
  • the difference between FIG. 1 b and FIG. 1 a is in FIG.
  • 1 b via 214 is formed in substrate 100 by plasma etching using the disclosed iodine-containing etch compounds, which also deposit the polymer passivation layer 212 on the sidewalls of the via 214 .
  • the polymer passivation layer 212 also provides smoother sidewall, less bowing and less deformation at the bottom of the via 214 .
  • the polymer passivation layer 212 may however be easily removed or cleaned by dry or wet etch chemistries known in the art.
  • FIG. 1 c is a cross-sectional side view of the exemplary layers in the 3D NAND stack of FIG. 1 a showing particles 316 generated during alternating SiO/SiN layer etching in a 3D NAND stack.
  • the particles 316 generated on the sidewalls of the alternative SiO/SiN (i.e., 104 a / 104 b ) layers 104 as shown in FIG. 1 c may be minimized by using the disclosed iodine-containing etching compounds.
  • the difference between FIG. 1 c and FIG. 1 b is in FIG. 1 c the alternative SiO/SiN exposed sidewall has particles 316 generated during plasma etching. Applicants do not believe that the disclosed iodine-containing etching compounds will generate the particles 316 shown in FIG. 1 c.
  • FIG. 1 d is a cross-sectional side view of the exemplary layers in the 3D NAND stack of FIG. 1 a showing selective isotropic etching of the SiN layers 104 b exposed on the sidewall in the 3D NAND stack after the anisotropic etching process.
  • the SiN exposed sidewall in stack 100 may be etched selectively as shown in FIG. 1 d by using the disclosed iodine-containing etching compounds to selectively break the Si—N bonds in the SiN layers 104 b over the Si—O bond in the SiO layers 104 a forming a selective sidewall SiN etch 418 on the stack of SiO/SiN layers 104 in the via 214 .
  • FIG. 1 b is in FIG. 1 d SiN exposed on the alternative SiO/SiN sidewall is selectively etched by the disclosed iodine-containing etching compounds forming the selective sidewall SiN etch 418 .
  • the selective sidewall SiN etch 418 is performed by wet etching using mixtures with phosphoric acid. Replacing wet etch process with dry plasma etch processes is known to greatly improve the economics of semiconductor device fabrication process since wet etching requires moving the substrate to different wet etching equipment.
  • all etching, including the selective sidewall SiN etch of FIG. 1 d may be performed in one piece of etching equipment, which may reduce the cost of the semiconductor fabrication.
  • substrate 100 may include a stack of multiple layers thereon as shown in FIG. 2 .
  • FIG. 2 is a cross-sectional side view of exemplary layers in a DRAM stack to produce a DRAM memory.
  • a stack of four layers is located on top of a silicon wafer 102 .
  • a hardmask layer 106 is located on top of a large SiO layer 104 a .
  • An antireflective coating layer 108 is located on top of the hardmask layer 106 .
  • a pattern photoresist layer 110 is located on top of the antireflective coating 108 .
  • a SiON layer (not shown) may be present between the antireflective coating layer 108 and the hardmask layer 106 to transfer pattern in photoresist layer 110 to the hardmask layer 106 .
  • the stack of layers in FIG. 2 is provided for exemplary purposes only and that the disclosed iodine-containing etching compounds may be used to etch other stacks of layers, for example, for a stack where the hardmask layer 106 is replaced with a TiN layer.
  • the number of layers in the stack may vary (i.e., may include more or less than the layers depicted).
  • FIG. 3 a is a cross-sectional side view of exemplary layers showing photoresist pattern over SiO insulation layer surrounding a typical transistor device region to produce a transistor structure.
  • Substrate 600 may include a stack of four layers surrounding a transistor gate electrode region supported on the Silicon wafer 602 as shown in FIG. 3 a .
  • the transistor region shown in FIG. 3 a includes two doped silicon regions 606 acting as source and drain.
  • Transistor gate dielectric 614 is present underneath gate electrode 616 .
  • the whole transistor, i.e., transistor gate dielectric 614 and gate electrode 616 is surrounded by a thin SiN layer 608 which may later act as etch stop layer during contact etch.
  • Each transistor device region 616 / 606 is separated by SiO isolation regions 604 in the silicon wafer 602 to minimize electrical interference.
  • layer 602 may be located on top of a silicon oxide layer of the Silicon on Insulator (SOI) wafer.
  • SOI Silicon on Insulator
  • Another SiO layer 610 is deposited on the transistor and used to insulate any metal contact to the transistor device regions 606 .
  • Photoresist mask 612 is used to pattern the SiO layer 610 . Etching is performed using the disclosed iodine-containing etching compounds in plasma environment. The photoresist mask 612 serves as a template to etch the SiO layer 610 and etching is stopped on the SiN layer 608 as shown in FIG. 3 b.
  • FIG. 3 b is a cross-sectional side view of the exemplary layers of FIG. 3 a after etching the SiO insulation layer.
  • the difference between FIG. 3 b and FIG. 3 a is in FIG. 3 b vias 718 are formed in the SiO layer 610 through etching by the disclosed iodine-containing etching compounds.
  • the SiO layer 610 may be etched with photoresist layer 612 as a mask layer.
  • the mask layer may be any suitable photoresist mask materials, such as TiN, a-C and so on. The etching may be stopped at the underlying SiN layer 608 .
  • the disclosed iodine-containing etching compounds may also be used to etch the SiN layer 608 with different plasma conditions and different mixtures.
  • the stack and geometry of layers in FIG. 3 a and FIG. 3 b is provided for exemplary purposes only and that the disclosed iodine-containing etching compounds may be used to etch other types of stacks of layers.
  • the number of layers in the stack may vary (i.e., may include more or less than the four layers depicted).
  • the vapor of the disclosed iodine-containing etching compounds is introduced into the reaction chamber containing the substrate and silicon-containing films.
  • the vapor may be introduced to the chamber at a flow rate ranging from approximately 0.1 sccm to approximately 1 slm.
  • the vapor may be introduced to the chamber at a flow rate ranging from approximately 5 sccm to approximately 50 sccm.
  • the vapor may be introduced to the chamber at a flow rate ranging from approximately 25 sccm to approximately 250 sccm.
  • the flow rate may vary from tool to tool.
  • the disclosed iodine-containing etching compounds may be supplied either in neat form or in a blend with an inert gas, such as N 2 , Ar, Kr, Ne He, Xe, etc., or solvent.
  • the disclosed iodine-containing etching compounds may be present in varying concentrations in the blend.
  • the vapor form of the iodine-containing etching compounds may be produced by vaporizing the neat or blended iodine-containing etching compound solution through a conventional vaporization step such as direct vaporization or by bubbling.
  • the neat or blended iodine-containing etching compounds may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into the reactor.
  • the neat or blended iodine-containing etching compounds may be vaporized by passing a carrier gas into a container containing the disclosed iodine-containing etching compounds or by bubbling the carrier gas into the disclosed iodine-containing etching compounds.
  • the carrier gas may include, but is not limited to, Ar, He, N 2 , Kr, Xe, Ne and mixtures thereof. Bubbling with a carrier gas may also remove any dissolved oxygen present in the neat or blended iodine-containing etching compound solution The carrier gas and disclosed iodine-containing etching compounds are then introduced into the reactor as a vapor.
  • the container containing the disclosed iodine-containing etching compounds may be heated to a temperature that permits the iodine-containing etching compounds to be in liquid phase and to have a sufficient vapor pressure for delivery into an etching tool.
  • the container may be maintained at temperatures in the range of, for example, approximately 0° C. to approximately 150° C., preferably from approximately 25° C. to approximately 100° C., more preferably from approximately 25° C. to approximately 50° C. More preferably, the container is maintained at room temperature (approximately 25° C.) in order to avoid heating lines to the etch tool.
  • the temperature of the container may be adjusted in a known manner to control the amount of iodine-containing etching compound vaporized.
  • the iodine-containing etching compounds are delivered in purity ranging from 95% to 99.999% by volume and may be purified with known standard purification techniques for removal of CO, CO 2 , N 2 , H 2 O, HF, H 2 S, SO 2 , halides, and other hydrocarbons or hydrohalocarbons.
  • An inert gas is also introduced into the reaction chamber in order to sustain the plasma.
  • the inert gas may be He, Ar, Xe, Kr, Ne, N 2 , He or combinations thereof.
  • the etching gas and the inert gas may be mixed prior to introduction to the chamber, with the inert gas comprising between approximately 0.01% v/v and approximately 99.9% v/v of the resulting mixture.
  • the inert gas may be introduced to the chamber continuously while the etching gas is introduced to the chamber in pulses.
  • the vapor of the disclosed etching gas and inert gas are activated by plasma to produce an activated etching gas.
  • the plasma decomposes the etching gas into radical form (i.e., the activated etching gas).
  • the plasma may be generated by applying RF or DC power.
  • the plasma may be generated with a RF power ranging from about 25 W to about 100,000 W.
  • the plasma may be generated remotely or within the reactor itself.
  • the plasma may be generated in dual CCP or ICP mode with RF applied at both electrodes.
  • RF frequency of plasma may range from 100 KHz to 1 GHz. Different RF sources at different frequency may be coupled and applied at same electrode. Plasma RF pulsing may be further used to control molecule fragmentation and reaction at substrate.
  • One of skill in the art will recognize methods and apparatus suitable for such plasma treatment.
  • a quadrupole mass spectrometer may measure the activated etching gas from the chamber exhaust to determine the types and numbers of species produced. If necessary, the flow rate of the etching gas and/or the inert gas may be adjusted to increase or decrease the number of radical species produced.
  • the disclosed etching gases may be mixed with other gases either prior to introduction into the reaction chamber or inside the reaction chamber.
  • the gases may be mixed prior to introduction to the chamber in order to provide a uniform concentration of the entering gas.
  • the vapor of the iodine-containing etching compound may be introduced into the chamber independently of the other gases, such as when two or more of the gases react or are easier to deliver independently.
  • the etching gas and the inert gas are the only two gases that are used during the etching process.
  • Exemplary other gases include, without limitation, oxidizers such as O 2 , O 3 , CO, CO 2 , NO, N 2 O, NO 2 , H 2 O, H 2 O 2 , COS, SO 2 and combinations thereof.
  • oxidizers such as O 2 , O 3 , CO, CO 2 , NO, N 2 O, NO 2 , H 2 O, H 2 O 2 , COS, SO 2 and combinations thereof.
  • the disclosed etching gases and the oxidizer may be mixed together prior to introduction into the reaction chamber.
  • the oxidizer may be introduced continuously into the chamber and the etching gas introduced into the chamber in pulses.
  • the oxidizer may comprise between approximately 0.01% v/v to approximately 99.99% v/v of the mixture introduced into the chamber (with 99.99% v/v representing introduction of almost pure oxidizer for the continuous introduction alternative).
  • exemplary gases with which the disclosed iodine-containing etching compounds may be used include additional etching gases, such as cC 4 F 8 , C 4 F 8 , cC 5 F 8 , C 5 F 8 , C 4 F 6 , CF 4 , CH 3 F, CF 3 H, CH 2 F 2 , C 3 HF 7 , C 3 F 6 , C 3 H 2 F 6 , C 3 H 2 F 4 , C 3 H 2 F 5 , C 4 HF 7 .
  • approximately 1% v/v to approximately 25% v/v of the disclosed iodine-containing etching compound may be used with a balance of C 4 F 6 or cC 4 F 8 .
  • the combination of the disclosed iodine-containing etching compounds with conventional etch gases may result in increased etch rates while maintaining the higher selectivity between the substrate and layer to be etched associated with the disclosed iodine-containing etching compounds.
  • the vapor of the disclosed iodine-containing etching compounds and the etching gas may be mixed prior to introduction to the reaction chamber.
  • the additional etching gas may comprise between approximately 0.01% v/v to approximately 99.99% v/v of the mixture introduced into the chamber.
  • the vapor of a disclosed iodine-containing compound such as C 4 F 9 I
  • a controlled gas flow device may be a mass flow controller or a bubbler design with inert gas flow to deliver the vapor of the desired molecule.
  • a special low pressure drop mass flow controller from Brooks Automation (No. GF120XSD), MKS Instruments, etc., may be used.
  • the pressure of the reaction chamber is set at approximately 30 mTorr. No gas source heating may be necessary if the vapor pressure is sufficient.
  • the distance between the two CCP electrodes is kept at 1.35 cm and the top electrode RF power is fixed at 750 W.
  • the bottom electrode RF power is varied to analyze the performance of the molecule.
  • the reaction chamber contains a substrate having silicon-containing films thereon, similar to those shown in FIG. 1 a .
  • the antireflective coating layer 108 is patterned/etched by a fluorocarbon (e.g., CF 4 and CH 2 F 2 ) and oxygen-containing gas (e.g., O 2 ).
  • the amorphous carbon mask layer is patterned/etched by an oxygen-containing gas.
  • the SiO and SiN layers 104 are patterned by the plasma of the disclosed iodine-containing etching compounds (e.g., C 4 F 9 I) and Argon.
  • Argon is independently introduced into the chamber at a 250 sccm flow rate.
  • C 4 F 9 I is independently introduced into the chamber at 15 sccm.
  • O 2 is independently introduced into the chamber and varied from 0 sccm to 20 sccm to determine optimum etching conditions.
  • An aperture having an aspect ratio equal to or greater than 10:1 is produced, which may be used as a channel hole or contact hole or staircase etch, slit etch in 3D NAND. Similar example may be used for other stack layers as shown in FIGS. 2 and 3 a.
  • C 4 F 9 I is introduced into a 200 mm Dual CCP plasma etch tool using a controlled gas flow device.
  • the controlled gas flow device may be a mass flow controller. In case of high boiling point molecules, a special low pressure drop mass flow controller from Brooks Automation (No. GF120XSD), MKS Instruments, etc., may be used.
  • the pressure of the reaction chamber is set at approximately 30 mTorr. No gas source heating may be necessary if the vapor pressure is sufficient.
  • the distance between the two CCP electrodes is kept at 1.35 cm and the top electrode RF power is fixed at 750 W. The bottom electrode RF power is varied to analyze the performance of C 4 F 9 I.
  • the reaction chamber contains a substrate 100 having a thick SiO layer 104 a thereon, similar to the layer shown in FIG. 2 .
  • the antireflective coating layer 108 is removed by a fluorocarbon (e.g., CF 4 ) and oxygen-containing gas (e.g., O 2 ) and the A-c mask layer 106 is removed by an oxygen-containing gas.
  • Argon is independently introduced into the chamber at a 250 sccm flow rate.
  • C 4 F 9 I is independently introduced into the chamber at 15 sccm.
  • 02 is independently introduced into the chamber at 0-20 sccm to determine optimum etching conditions.
  • An aperture having an aspect ratio equal to or greater than 10:1 is produced, which may be used as a contact hole in DRAM. Similar examples may be used for other stack layers as shown in FIGS. 1 a and 3 a.
  • the silicon-containing films and the activated iodine-containing etching gas react to form volatile by-products that are removed from the reaction chamber.
  • the a-C mask, antireflective coating, and photoresist layer are less reactive with the activated etching gas.
  • the activated etching gas selectively reacts with the silicon-containing films to form volatile by-products.
  • the temperature and the pressure within the reaction chamber are held at conditions suitable for the silicon-containing film to react with the activated etching gas.
  • the pressure in the chamber may be held between approximately 0.1 mTorr and approximately 1000 Torr, preferably between approximately 1 mTorr and approximately 10 Torr, more preferably between approximately 10 mTorr and approximately 1 Torr, and more preferably between approximately 10 mTorr and approximately 100 mTorr, as required by the etching parameters.
  • the substrate temperature in the chamber may range between about approximately ⁇ 196° C. to approximately 500° C., preferably between approximately ⁇ 120° C. to approximately 300° C., more preferably between approximately ⁇ 100° C. to approximately 50° C.; and more preferably between approximately ⁇ 10° C. to approximately 40° C.
  • Chamber wall temperatures may range from approximately ⁇ 196° C. to approximately 300° C. depending on the process requirements.
  • the reactions between the silicon-containing film and the activated etching gas result in anisotropic removal of the silicon-containing films from the substrate.
  • Atoms of nitrogen, oxygen, and/or carbon may also be present in the silicon-containing film.
  • the removal is due to a physical sputtering of silicon-containing film from plasma ions (accelerated by the plasma) and/or by chemical reaction of plasma species to convert Si to volatile species, such as SiF x , wherein x ranges from 1-4.
  • the plasma activated vapor of the disclosed iodine-containing etching compounds preferably exhibits high selectivity toward the mask and etches through the alternating layers of SiO and SiN resulting in a vertical etch profile with no bowing or roughness, which is important for 3D NAND applications. Additionally, plasma activated vapor deposits polymer on sidewall to minimize feature profile deformation. For other applications, such as DRAM and 2D NAND, for example, the plasma activated etching gas under different process conditions may selectively etch SiO from SiN.
  • the plasma activated etching gas may selectively etch SiO and/or SiN from mask layers, such as a-C, photoresist, p-Si, or silicon carbide; or from metal contact layers, such as Cu, W, Ru, etc.; or from channel regions consisting of SiGe or polysilicon regions.
  • the disclosed etch processes using the disclosed iodine-containing etching compounds as the etching gases produce channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, contact etch, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films.
  • the resulting aperture may have an aspect ratio ranging from approximately 10:1 to approximately 200:1 and a diameter ranging from approximately 5 nm to approximately 500 nm, preferably less than 100 nm.
  • a channel hole etch produces apertures in the silicon-containing films having an aspect ratio greater than 50:1.
  • Typical materials that need to be etched may be SiO.
  • a process of etching SiO may be relevant to etching trenches in Borophosphosilicateglass (BPSG), Tetraethylorthosilicate (TEOS), or low deposition rate TEOS (LDTEOS).
  • An etch stop layer may be silicon nitride or silicon oxygen nitride (SiON) or poly silicon.
  • a mask material used may be a-C, p-Si, or photo resist materials.
  • the disclosed iodine-containing etching compounds are applied to etch SiO, SiN, p-Si and/or a-C substrate films.
  • the iodine is ionized and bombards the surface with the heavy I ion similar to inert gases such as Ar, Kr, and Xe.
  • the iodine ionized atoms modifies the surface of the organic hard mask, by doping it and improving its etch resistance, so as to favor high aspect ratio etch.
  • the activated iodine-containing etching compound produces iodine ions, which strengthens the patterned mask layer, thereby reinforcing and minimizing damage to a patterned mask layer while forming a patterned structure in the substrate.
  • etching gas results presented herein show they are not only ready for patterned structure etch process, such as contact etch process, but also may be beneficial for other etching processes on silicon or metal containing substrates, including low k etching processes.
  • an etch resistance of the pattern mask layer may be increased by doping iodine to the surface of the pattern mask layer, thereby modifying the surface.
  • the iodine ions from the activated iodine-containing etching compound are implanted into the patterned mask layer (i.e., the surface and/or the body/bulk of the patterned mask layer) while etching the silicon-containing film from the substrate to form the patterned structure.
  • the disclosed iodine-containing etching compounds are suitable for reduction of the global warming potential caused by perfluorocarbon compounds.
  • amorphous carbon (a-C) on Si substrate 350 PECVD amorphous carbon (a-C) on Si substrate.
  • etch rate were measured using an Ellipsometer and/or scanning electron microscope (SEM) by measuring the change in etch thickness as a function of etching time.
  • SEM scanning electron microscope
  • the etching experiment were performed on four 1.5 ⁇ 1.5 cm 2 coupons having four different substrate materials including SiO, SiN, p-Si and a-C, listed above.
  • the coupons are placed on 200 mm diameter carrier wafer and held in contact by using silicon oil or thermal paste.
  • double sided carbon tape obtained from 2 spi manufacturer may have been used to stick coupons on carrier wafer.
  • Etching tests were performed at a pressure of 30 mTorr, source power of 750 W (27 MHz), bias power of 1500 W (2 MHz), and temperature 20° C.
  • the feed mixture contains 250 sccm of Ar, 15 sccm of etch gas, while 02 is varied in the range 0 to 20 sccm.
  • FIG. 4 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C 3 F 7 I (CAS No. 754-34-7), O 2 and Ar.
  • the y-axis represents etch rates; the x-axis is O 2 flow rate in sccm; the 1-C 3 F 7 I flow rate is fixed at 15 sccm, the Ar is fixed at 250 sccm while the O 2 flow rate is varied from 0 to 20 sccm.
  • SiO 2 ER decreases as O 2 flow rate increase, while SiN, p-Si and a-C ERs increase as O 2 flow rate increases.
  • the highest selectivity meaning the ratio between SiO ER and other materials ER rate is shown when no oxygen is flown.
  • SiO 2 /a-C selectivity is 38.5
  • SiO 2 /p-Si selectivity is 22, and SiO 2 /SiN selectivity is 11.
  • FIG. 5 is a graph demonstrating the electron impact ionization energy (eV) versus species concentration (Torr) of C 3 F 7 I.
  • the dominant fragments produced at between 10 and 20 eV are CF 3 , C 3 F 7 , and I.
  • FIG. 6 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C 4 F 9 I, O 2 and Ar.
  • the y-axis represents etch rates;
  • the x-axis is O 2 flow rate in sccm;
  • the 1-C 4 F 9 I flow rate is fixed at 15 sccm,
  • the Ar is fixed at 250 sccm while the O 2 flow rate is varied from 0 to 20 sccm.
  • SiO 2 ER decreases as O 2 flow rate increases, while SiN, p-Si and a-C ERs increase as O 2 flow rate increases.
  • the highest selectivity meaning the ratio between SiO ER and other materials ER rate is shown when no oxygen is flown.
  • SiO 2 /a-C selectivity is 71
  • SiO 2 /p-Si selectivity is 47
  • SiO 2 /SiN selectivity is 17. Comparing to the results of 1-C 3 F 7 I shown in FIG. 4 , 1-C 4 F 9 I is better than 1-C 3 F 7 I both in terms of SiO 2 ER and selectivity of SiO 2 vs all the other materials tested.
  • FIG. 10 and FIG. 11 are graphs demonstrating etch rates of SiO, SiN, p-Si and a-C with cC 4 F 8 and C 4 F 6 , respectively.
  • XPS angle resolved at 75° sample tilting and depth profile were performed to analyze the polymer composition on a-C masks and benchmarked with SiO 2 substrate.
  • a-C mask Boron-doped a-C [a-C(B)] and Tungsten-doped a-C [a-C(W)] and SiO 2 (TEOS) coupons were etched at 30 mTorr for 60 sec, source power 750 W (27 MHz), and bias power 1500 W (2 MHz) at the substrate.
  • the process feed the mixture contains 125 sccm of Ar, 30 sccm of 1-C 4 F 9 I and no O 2 .
  • the neutrals and the active species reaching the surface stick to the surface, based on their sticking coefficient, and deposit a thin polymer layer. This thin polymer layer may be responsible for sidewall passivation and often provides the selectivity.
  • Table 4 to Table 6 are XPS angle resolved at 75° on different a-C layers after 1-C 4 F 9 I etching.
  • Depth profile on a-C substrate Superficial atomic concentration (%) is listed in Table 7 and FIG. 7 .
  • Depth profile on a-C(B) substrate Superficial atomic concentration (%) is listed in Table 8 and FIG. 8 .
  • Depth profile on a-C(W) substrate Superficial atomic concentration (%) is listed in Table 9 and FIG. 9 .
  • Superficial atomic concentration after 1-C 4 F 9 I etch on SiO 2 substrate is listed in Table 10.
  • the disclosed Iodine-containing etching compound show an interesting behavior during a-C mask etch compared to etch of Si-based materials. According to XPS data, Iodine penetrates deeply on a-C mask, similar to a doping effect, helping preserving it during etch.
  • This example shows that Iodine ions modify the surface of the pattern mask by depositing a polymer layer composed of C x F y I z atoms as well as the iodine ions penetrate deep into the bulk of the pattern mask layer.
  • the iodine-containing etching compounds help preserving the pattern mask layer by increasing the crosslinking with the organic layer, making the pattern mask stronger and increasing its etch resistance.

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Abstract

Disclosed are methods for etching a silicon-containing film to form a patterned structure, methods for reinforcing and/or strengthening and/or minimizing damage of a patterned mask layer while forming a patterned structure and methods for increasing etch resistance of a patterned mask layer in a process of forming a patterned structure. The methods include using an activated iodine-containing etching compound having the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4 as an etching gas. The activated iodine-containing etching compound produces iodine ions, which are implanted into the patterned hardmask layer, thereby strengthening the patterned mask layer.

Description

    TECHNICAL FIELD
  • Methods for etching a silicon-containing film to form a patterned structure, methods for reinforcing and/or strengthening and/or minimizing damage of a patterned mask layer while forming a patterned structure and methods for increasing etch resistance of a patterned mask layer in a process of forming a patterned structure using iodine-containing etching compounds are disclosed. The iodine-containing etching compound have the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4.
    • BACKGROUND
  • In semiconductor industries, for 3D NAND, etching of stacks of multiple SiO/SiN or SiO/poly-Silicon (p-Si) layers is critical. See, e.g., US 2011/0180941 to Samsung Electronics Co., Ltd. An etchant having high selectivity between the mask and layers being etched is essential. Furthermore, the etched structure should have a straight vertical profile without bowing and low line etch roughness (LER).
  • Traditional etch gases include octafluorocyclobutane (cC4F8), hexafluoro-1,3-butadiene (C4F6), CF4, CH2F2, CH3F, and/or CHF3. It is well known that selectivity and polymer deposition rate increase as the ratio of C:F increases (i.e., C4F6>C4F8>CF4). See, e.g., U.S. Pat. No. 6,387,287 to Hung et al. In addition, other gases, such as inert gases like Ar, Kr, or Xe, are added to the plasma where they are ionized and accelerated to the wafer surface bombarding the surface and supporting the etching process. Because they are inert gases, they do not directly participate in the chemical reactions of the etching process.
  • However, traditional etch chemistries may not be able to provide a feature, such as a hole or trench, having an aspect ratio higher than 20:1, which is necessary in the newer applications (e.g., 3D NAND), at least due to insufficient etch resistant polymer deposition on sidewalls during the plasma etching processes. The sidewall —CxFy— polymers, wherein x ranges from 0.01 to 1 and y ranges from 0.01 to 4, may be susceptible to etching. As a result, the etched patterns may not be vertical and the etch structures may show bowing, change in dimensions, pattern collapse and/or increased roughness.
  • Bowing may result from sidewall etching of the mask layer, which may often be an amorphous carbon (a-C) material. The a-C materials may be etched by oxygen radicals in the plasma which may cause increased opening of the mask and result in bow-like, or angled/curved, etch structures.
  • Iodine-containing compounds have been used as etching gases and/or reduction of global warming potential (GWP). For example, Gupta et al. (U.S. Pat. No. 10,607,850) disclose the iodine-containing etching compound has the formula CaHxFyIz, wherein a=1-3, x=0-6, y=1-7, z=1-2, x+y+z=4 when a=1, x+y+z=4 or 6 when a=2, x+y+z=6 or 8 when a=3. Chung (U.S. Pat. No. 9,460,935) discloses etching first and second etching layers under plasma generated using, among others, 1,1,2,2-tetrafluoro-1-iodo-ethane. See also Karecki et al., “Plasma etching of dielectric films with novel iodofluorocarbon chemistries: iodotrifluoroethylene and 1-iodoheptafluoropropane”, J. Vac. Sci. Technol. A 16, 755 (1998); JP2006/108484; and TWI343601. Iodine-containing etching compounds have been shown significant reductions in global warming emissions compared to perfluorocarbon compounds (see S. Karecki, L. Pruette, and R. Reif, J. Electrochem. Soc. 145, 4305 (1998))
  • It is important to minimize bowing and to achieve high aspect ratio (i.e., up to 200:1) needed for current applications (e.g., contact etch or 3D NAND). Additionally, etching today has not been limited to selectivity to the photoresist mask. It is equally important to get high selectivity among other materials such as a-C, SiN, p-Si, SiC or other forms of SiaCbOcHdNe materials (where a>0; b, c, d and e≥20).
  • Thus, a need remains for etch gas compositions suitable for use in plasma etching applications which maintain selectivity and high aspect ratios for a wide range of process conditions.
    • SUMMARY
  • Disclosed are methods of forming a patterned structure, the method comprising:
  • introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and a patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4;
  • activating a plasma to produce an activated iodine-containing etching compound; and
  • allowing an etching reaction to proceed between the activated iodine-containing etching compound and the silicon-containing film to selectively etch the silicon-containing film from the patterned mask layer, thereby forming the patterned structure. The disclosed methods may include one or more of the following aspects:
      • further comprising introducing an oxidizer into the reaction chamber;
      • the oxidizer being selected from O2, O3, CO, CO2, NO, N2O, NO2, H2O, H2O2. COS, SO2 and combinations thereof;
      • the oxidizer being O2;
      • further comprising introducing an inert gas into the reaction chamber;
      • the inert gas being selected from the group consisting of He, Ar, Xe, Kr, Ne and N2;
      • the inert gas being Ar;
      • the inert gas being Xe;
      • the inert gas being Kr;
      • the iodine-containing etching compound being a hydrofluorocarbon compound;
      • the iodine-containing etching compound being an organofluorine compound:
      • the iodine-containing etching compound being a fluorine-containing hydrocarbon compound;
      • the iodine-containing etching compound being a fluorocarbon compound;
      • the iodine-containing etching compound being a hydrocarbon compound;
      • the iodine-containing etching compound containing no hydrogen;
      • the iodine-containing etching compound containing hydrogen;
      • the iodine-containing etching compound containing fluorine;
      • the iodine-containing etching compound containing no fluorine;
      • the iodine-containing etching compound being C4F9I, C5F11I, C6F13I, C7F15I, C8F17I, C9F19I, C10F21I or their isomers;
      • the iodine-containing etching compound being C4HF8I, C5HF10I, C6HF12I, C7HF14I, C8HF16I, C9HF18I, C10HF20I, C4HF8I, C5HF8I, C6HF10I, C7HF12I, C8HF14I, C9HF16I, C10HF18I, C4HF4I, C5HF6I, C6HF8I, C7HF10I, C8HF12I, C9HF14I, C10HF16I, C4HF7I2, C5HF9I2, C6HF11I2, C7HF13I2, C8HF15I2, C9HF17I2, C10HF19I2, C4HF5I2, C5HF7I2, C6HF9I2, C7HF11I2, C8HF13I2, C9HF15I2, C10HF17I2, C4HF3I2, C5HF5I2, C6HF7I2, C7HF9I2, C8HF11I2, C9HF13I2, C10HF15I2, C4HF6I3, C5HF8I3, C6HF10I3, C7HF12I3, C8HF14I3, C9HF16I3, C10HF18I3, C4HF4I3, C5HF6I3, C5HF8I3, C7HF10I3, C8HF12I3, C9HF14I3, C10HF16I3, C4HF5I4, C5HF7I4, C6HF9I4, C7HF11I4, C8HF13I4, C9HF15I4, C10HF17I4. C4HF3I4, C5HF5I4, C6HF7I4, C7HF9I4, C8HF11I4, C9HF13I4, C10HF15I4, C4HFI4, C5HF3I4, C6HF5I4, C7HF7I4, C8HF9I4, C9HF11I4, C10HF13I4 or their isomers;
      • the iodine-containing etching compound being C4H2F7I, C5H2F9I, C6H2F11I, C7H2F13I, C8H2F15I, C9H2F17I, C10H2F19I, C4H2F5I, C5H2F7I, C6H2F9I, C7H2F11I, C8H2F13I, C9H2F15I, C10H2F17I, C4H2F6I2, C5H2F8I2, C6H2F10I2, C7H2F12I2, C8H2F14I2, C9H2F16I2, C10H2F15I2, C4H2F4I2, C5H2F6I2, C6H2F8I2, C7H2F10I2, C8H2F12I2, C9H2F14I2, C10H2F16I2, C4H2F5I3, C5H2F7I3, C6H2F9I3, C7H2F11I3, C8H2F13I3, C9H2F15I3, C10H2F17I3, C4H2F3I3, C5H2F5I3, C6H2F7I3, C7H2F9I3, C8H2F11I3, C9H2F13I3, C10H2F15I3, C4H2F4I4, C5H2F6I4, C6H2F8I4, C7H2F10I4, C8H2F12I4, C9H2F14I4, C10H2F16I4, C4H2F2I4, C5H2F4I4, C6H2F6I4, C7H2F8I4, C8H2F10I4, C9H2F12I4, C10H2F14I4 or their isomers;
      • the iodine-containing etching compound being C4H3F6I, C5H3F8I, C6H3F10I, C7H3F12I, C8H3F14I, C9H3F16I, C10H3F18I, C4H3F4I, C5H3F6I, C6H3F8I, C7H3F10I, C8H3F12I, C9H3F14I, C10H3F16I, C4H3F5I2, C5H3F7I2, C6H3F9I2, C7H3F11I2, C8H3F13I2, C9H3F15I2, C10H3F17I2, C4H3F3I2, C5H3F5I2, C6H3F7I2, C7H3F9I2, C8H3F11I2, C9H3F13I2, C10H3F15I2, C4H3F4I3, C5H3F6I3, C6H3F8I3, C7H3F10I3, C8H3F12I3, C9H3F14I3, C10H3F16I3, C4H3F2I3, C5H3F4I3, C6H3F6I3, C7H3F8I3, C8H3F10I3, C9H3F12I3, C10H3F14I3, C4H3F3I4, C5H3F5I4, C6H3F7I4, C7H3F9I4, C8H3F11I4, C9H3F13I4, C10H3F15I4, C4H3F1I4, C5H3F3I4, C6H3F5I4, C7H3F7I4, C8H3F9I4, C9H3F11I4, C10H3F13I4 or their isomers;
      • the iodine-containing etching compound being C4H4F5I, C5H4F7I, C6H4F9I, C7H4F11I, C8H4F13I, C9H4F15I, C10H4F17I, C4H4F3I, C5H4F5I, C6H4F7I, C7H4F9I, C8H4F11I, C9H4F13I, C10H4F15I, C4H4F4I2, C5H4F6I2, C6H4F8I2, C7H4F10I2, C8H4F12I2, C9H4F14I2, C10H4F16I2, C4H4F2I2, C5H4F4I2, C6H4F6I2, C7H4F8I2, C8H4F10I2, C9H4F12I2, C10H4F14I2, C4H4F3I3, C5H4F5I3, C6H4F7I3, C7H4F9I3, C8H4F11I3, C9H4F13I3, C10H4F15I3, C4H4FI3, C5H4F3I3, C6H4F5I3, C7H4F7I3, C8H4F9I3, C9H4F11I3, C10H4F13I3, C4H4F2I4, C5H4F4I4, C6H4F6I4, C7H4F8I4, C8H4F10I4, C9H4F12I4, C10H4F14I4, C4H4I4, C5H4F2I4, C6H4F4I4, C7H4F6I4, C8H4F8I4, C9H4F10I4, C10H4F12I4 or their isomers;
      • the iodine-containing etching compound being C4F9I or its isomers;
      • the plasma activated the iodine-containing etching compound reacting with the silicon-containing film to form volatile by-products;
      • the volatile by-products being removed from the reaction chamber;
      • the silicon-containing film comprising oxygen, nitrogen, carbon, hydrogen, carbon or combinations thereof;
      • the silicon-containing film being comprising a layer of silicon oxide (SiO), silicon nitride (SiN), crystalline Si, poly-silicon (p-Si), polycrystalline silicon, amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON and SiaObHcCdNe, where a>0; b, c, d and e≥0, alternating SiO and SiN (ONON) layers, alternating SiO and p-Si (OPOP) layers;
      • the silicon-containing film optionally containing dopants such as B, C, P, As, Ga, In, Sn, Sb, Bi and/or Ge, or combinations thereof;
      • the silicon-containing film comprising oxygen, nitrogen, carbon, hydrogen, or combinations thereof;
      • the silicon-containing film being SiOxNyHzCk, wherein x ranges from 0 to 2, y ranges from 0 to 4, z ranges from 0 to about 1 and k ranges from 0 to 1;
      • the silicon-containing film comprising a SiO layer;
      • the silicon-containing film being a SiN layer,
      • the silicon-containing film comprising alternating SiO and SiN (ONON) layers;
      • the silicon-containing film comprising alternating SiO and p-Si (OPOP) layers;
      • the silicon-containing film comprising dopants such as B, C, P, As, Ga, In, Sn, Sb, Bi and/or Ge;
      • the alternating layers comprising a layer of silicon oxide, silicon nitride, polysilicon, crystalline silicon, SiOCH, SiON, SiaObCcNdHe (where a>0; b, c, d and e≥0) or combinations thereof;
      • the alternating layers comprising oxygen atoms, nitrogen atoms, carbon atoms, hydrogen atoms or combinations thereof;
      • the alternating layers being a silicon containing film;
      • the alternating layers comprising a layer of silicon oxide and a layer of silicon nitride;
      • the alternating layers comprising alternating layers of silicon oxide and silicon nitride;
      • the alternating layers being alternating layers of silicon oxide and silicon nitride;
      • the alternating layers comprising a layer of silicon oxide and a layer of polysilicon;
      • the alternating layers comprising alternating layers of silicon oxide and polysilicon;
      • the alternating layers being alternating layers of silicon oxide and polysilicon;
      • a hardmask layer being disposed on the silicon-containing layer;
      • the hardmask layer being a patterned hardmask layer;
      • the hardmask layer being an amorphous carbon layer, a doped amorphous carbon layer, a photoresist layer, an anti-reflective layer, an organic planarization layer or combinations thereof;
      • the hardmask layer being a layer of CVD, PECVD, ALD, PEALD or spin on deposited (SOD) amorphous carbon or doped amorphous carbon, silicon-containing spin on mask, or carbon-containing spin on mask;
      • the hardmask layer being an amorphous carbon (a-C) layer;
      • the hardmask layer being a doped carbon layer;
      • the doped amorphous carbon layer being a boron-doped a-C layer;
      • the doped amorphous carbon layer being a tungsten-doped a-C layer;
      • the alternating layers being selectively etched from the hardmask layer;
      • the alternating layers being selectively etched from an a-C layer;
      • the alternating layers being selectively etched from a doped carbon layer;
      • the alternating layers of silicon oxide and silicon nitride being selectively etched from an a-C layer;
      • the alternating layers of silicon oxide and silicon nitride being selectively etched from a doped carbon layer;
      • the alternating layers of silicon oxide and polysilicon being selectively etched from an a-C layer;
      • the alternating layers of silicon oxide and polysilicon being selectively etched from a doped carbon layer;
      • the silicon oxide layer being selectively etched from the hardmask layer;
      • the silicon oxide layer being selectively etched from an a-C layer;
      • the silicon oxide layer being selectively etched from a doped carbon layer;
      • the silicon nitride layer being selectively etched from the hardmask layer;
      • the silicon nitride layer being selectively etched from an a-C layer;
      • the silicon nitride layer being selectively etched from a doped carbon layer;
      • the polysilicon layer being selectively etched from the hardmask layer;
      • the polysilicon layer being selectively etched from an a-C layer;
      • the polysilicon layer being selectively etched from a doped carbon layer,
      • the silicon-containing film being selectively etched from an amorphous carbon layer, a doped amorphous carbon layer, a photoresist layer, an anti-reflective layer or organic planarization layer;
      • the silicon oxide layer is selectively etched from an amorphous carbon layer, a doped amorphous carbon layer, a photoresist layer, an anti-reflective layer or organic planarization layer;
      • the iodine-containing etching compound etching both the silicon oxide layer and the silicon nitride layer with high etch rates;
      • the selectivity of the iodine-containing etching compound etching both silicon oxide layer and the silicon nitride layer ranging from approximately 1:2 to approximately 2:1;
      • the iodine-containing etching compound plasma etching the alternating SiO and SiN (ONON) layers having a selectivity between approximately 1:2 to approximately 2:1 with respect to the SiO layer versus SiN layer:
      • the iodine-containing etching compound plasma etching the alternating SiO and SiN (ONON) layers having a selectivity of approximately 1:1 with respect to the SiO layer versus SiN layer;
      • the selectivity of the iodine-containing etching compound etching both silicon oxide layer and the silicon nitride layer being approximately 1:1;
      • the iodine-containing etching compound etching both the silicon oxide layer and the polysilicon layer with high etch rates;
      • the selectivity of the iodine-containing etching compound etching both silicon oxide layer and the polysilicon layer ranging from approximately 1:2 to approximately 2:1;
      • the iodine-containing etching compound plasma etching the alternating SiO and p-Si (OPOP) layers having a selectivity between approximately 1:2 to approximately 2:1 with respect to the SiO layer versus p-Si layer;
      • the iodine-containing etching compound plasma etching the alternating SiO and p-SI (OPOP) layers having a selectivity of approximately 1:1 with respect to the SiO layer versus p-Si layer;
      • the selectivity of the iodine-containing etching compound etching both silicon oxide layer and the polysilicon layer being approximately 1:1;
      • an etch rate of etching the silicon oxide layer using the iodine-containing etching compound being higher than an etch rate of etching the silicon oxide layer using the traditional etching gases cC4F8, C4F6 CF4. CH3F, CF3H, CH2F2, or combinations thereof;
      • an etch rate of etching the silicon oxide layer using the iodine-containing etching compound being approximately 640 nm/min;
      • an etch rate of etching the silicon oxide layer using the iodine-containing etching compound which is higher than the etch rate of etching the silicon oxide layer SiO2 using the traditional etching gas cC4F8;
      • an etch rate of etching the silicon oxide layer using the iodine-containing etching compound which is higher than the etch rate of etching the silicon oxide layer SiO2 using the traditional etching gas C4F6;
      • an etch rate of etching the silicon oxide layer using C4F9I which is higher than the etch rate of etching the silicon oxide layer SiO2 using etching gases cC4F8 or C4F6 with heating of the iodine-containing etching compound for plasma etching to avoid condensation;
      • an etch rate of etching the silicon oxide layer using C4F9I which is higher than the etch rate of etching the silicon oxide layer SiO2 using an etching gas cC4F8 with heating of the iodine-containing etching compound for plasma etching to avoid condensation;
      • an etch rate of etching the silicon oxide layer using C4F9I which is higher than the etch rate of etching the silicon oxide layer SiO2 using an etching gas C4F6 with heating of the iodine-containing etching compound for plasma etching to avoid condensation;
      • heating the iodine-containing etching compound for plasma etching to avoid condensation;
      • the patterned structure formed in the silicon-containing film has an aspect ratio between approximately 1:1 and approximately 200:1;
      • heating the iodine-containing etching compound for plasma etching to maintain a desired flow rate of the iodine-containing etching compound;
      • the iodine-containing etching compound selectively etching the silicon-containing film from a landing layer located at the bottom of the silicon-containing film to be etched;
      • the landing layer being a buried landing layer located at the bottom of the structure to be etched;
      • the landing layer being an etching stop layer;
      • the landing layer being a silicon layer;
      • the landing layer being a metal layer:
      • the landing layer being a tungsten metal worldline in a 3D NAND structure and/or another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Nb, Cr, Rh, Pd, Ir, V, Au, Ag or combinations thereof;
      • the landing layer being a metal oxide or metal nitride layer;
      • the landing layer being a AlO, WO, TiN, or TaN layer;
      • the metal layer being selected from W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, or an etch stop layer selected from AlO, WO, TiN, TaN;
      • the landing layer being a metal oxide layer or a metal nitride layer selected from AlO, WO, HfO, TiO, TaO, InO, WO, CrO, RuO, CoO, MoO, ZrO, SnO, TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN, ZrN, SrN or combinations thereof;
      • adding an oxygen containing gas to the iodine-containing etching compound;
      • the oxygen containing gas selected from the group consisting of O2, O3, CO, CO2, NO, NO2, N2O, SO2, COS, H2O and combination thereof,
      • the oxygen containing gas being 02;
      • mixing the iodine-containing etching compound and the oxygen containing gas prior to introduction to the chamber to produce a mixture;
      • introducing the iodine-containing etching compound separately from the oxygen containing gas;
      • introducing the oxygen containing gas continuously and introducing the iodine-containing etching compound;
      • the oxygen containing gas comprising approximately 0.01% v/v to approximately 99.9% v/v of a total volume of the iodine-containing etching compound and oxygen containing gas;
      • the oxygen containing gas comprising approximately 0.01% v/v to approximately 10% v/v of a total volume of the iodine-containing etching compound and oxygen containing gas;
      • mixing the iodine-containing etching compound and the inert gas prior to introduction to the chamber to produce a mixture;
      • introducing the iodine-containing etching compound separately from the inert gas;
      • introducing the inert gas continuously and introducing the iodine-containing etching compound in pulses:
      • the inert gas comprising approximately 0.01% v/v to approximately 99.9% v/v of a total volume of the vapor of the iodine-containing etching compound and inert gas;
      • the inert gas comprising approximately 90% v to approximately 99% v/v of a total volume of the vapor of the iodine-containing etching compound and inert gas;
      • the substrate being a Si wafer;
      • the substrate being a crystalline silicon layer;
      • forming the patterned structure;
      • the patterned structure being 3D NAND apertures;
      • the patterned structure being contact holes;
      • the patterned structure being 3D NAND contact holes;
      • the patterned structure being DRAM contact;
      • the patterned structure being channel holes;
      • the patterned structure being 3D NAND channel holes;
      • the patterned structure being 3D NAND slit contact;
      • the aperture being staircase contacts;
      • the aperture being self-aligned contact;
      • the aperture being self-aligned vias;
      • the aperture being super vias;
      • further comprising introducing an additional etch gas to the iodine-containing etching compound;
      • the additional etch gas being selected from the group consisting of the group consisting of cC4F8, C4F6, cC5F8, C5F8, C4F6, CF4, CH3F, CF3H, CH2F2, C3HF7, C3F6, C3H2F6, C3H2F4, C3H3F5, C4HF7. C5HF9. C3F6, C3F8, CF3I, C2F3I, C2F5I, C3F7I, 1-lodoheptafluoropropane (1-C3F7I), 2-lodoheptafluoropropane (2-C3F7I), C3HF7, COS, FNO, F—C≡N, CS2, SO2, SF6, trans-1,1,1,4,4,4-hexafluoro-2-butene (trans-C4H2F6), cis-1,1,1,4,4,4-hexafluoro-2-butene (cis-C4H2F6), hexafluoroisobutene (C4H2F6), trans-1,1,2,2,3,4-hexafluorocyclobutane (trans-C4H2F6), 1,1,2,2,3-pentafluorocyclobutane (C4H3F5), 1,1,2,2-tetrafluorocyclobutane (C4H4F4), and cis-1,1,2,2,3,4-hexafluorocyclobutane (cis-C4H2F6) or combination thereof;
      • introducing the iodine-containing etching compound separately from the additional etch gas;
      • adding approximately 0.01% v/v to approximately 99.99% v/v of the additional etch gas to the iodine-containing etching compound;
      • activating the plasma by applying RF power;
      • activating the plasma by a RF power ranging from approximately 25 W to approximately 100,000 W;
      • etching pressure ranging from approximately 1 mTorr to approximately 10 Torr;
      • etching pressure being 30 mTorr;
      • introducing the iodine-containing etching compound at a flow rate ranging from approximately 0.1 sccm to approximately 1 slm;
      • maintaining the substrate at a temperature ranging from approximately −196° C. to approximately 500° C.;
      • maintaining the substrate at a temperature ranging from approximately −120° C. to approximately 300° C.;
      • maintaining the substrate at a temperature ranging from approximately −100° C. to approximately 50° C.;
      • maintaining the substrate at a temperature ranging from approximately −10° C. to approximately 40° C.; and
      • measuring the iodine-containing etching compound under plasma by Quadrupole mass spectrometer, optical emission spectrometer, FTIR, or other radical/ion measurement tool.
  • Also disclosed are methods of reinforcing, strengthening and minimizing damage of a patterned mask layer while forming a patterned structure in a substrate, the method comprising:
  • introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and the patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4; and
  • etching the silicon-containing film from the patterned mask layer to form the patterned structure using an activated iodine-containing etching compound formed by activating a plasma,
  • wherein the activated iodine-containing etching compound produces iodine ions, which are implanted into the patterned hardmask layer, thereby strengthening the patterned mask layer. The disclosed methods may include one or more of the following aspects:
      • the iodine-containing etching compound being a fluorine-containing hydrocarbon compound;
      • the iodine-containing etching compound being a fluorocarbon compound;
      • the iodine-containing etching compound being an organofluorine compound;
      • the iodine-containing etching compound being a hydrocarbon compound;
      • the activated iodine-containing etching compound produces iodine ions that strengthens the patterned mask layer;
      • the iodine-containing etching compound is C4F9I, C5F11I, C6F13I, C7F15I, C8F17I, C9F19I C10F21I or their isomers; and
      • the iodine-containing etching compound is C4F9I or its isomers.
  • Also disclosed are increasing etch resistance of a pattern mask layer by doping with iodine the pattern mask layer and/or by modifying with iodine the surface of the pattern mask layer in a process of forming a patterned structure in a substrate, the method comprising:
  • introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and the patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4;
  • activating a plasma to produce an activated iodine-containing etching compound capable of doping iodine into the patterned mask layer, thereby modifying the patterned mask layer with iodine to increase the etch resistance of the patterned mask layer; and
  • implanting iodine ions from the activated iodine-containing etching compound into the patterned mask layer while etching the silicon-containing film from the patterned mask layer to form the patterned structure. The disclosed methods may include one or more of the following aspects:
      • the iodine-containing etching compound being a fluorine-containing hydrocarbon compound;
      • the iodine-containing etching compound being a fluorocarbon compound;
      • the iodine-containing etching compound being a hydrocarbon compound;
      • the iodine-containing etching compound being an organofluorine compound;
      • the iodine-containing etching compound is C4F9I, C5F11I, C6F13I, C7F15I, C8F17I, C9F19I and C10F21I or their isomers;
      • the iodine-containing etching compound is C4F9I or its isomers;
      • implanting the iodine ion from the activated iodine-containing etching compound into the surface and/or the bulk of the patterned mask layer while etching the silicon-containing film from the substrate to form the patterned structure;
      • implanting the iodine ion from the activated iodine-containing etching compound into the surface of the patterned mask layer while etching the silicon-containing film from the substrate to form the patterned structure; and
      • implanting the iodine ion from the activated iodine-containing etching compound into the bulk of the patterned mask layer while etching the silicon-containing film from the substrate to form the patterned structure.
    Notation and Nomenclature
  • The following detailed description and claims utilize a number of abbreviations, symbols, and terms, which are generally well known in the art. While definitions are typically provided with the first instance of each acronym, for convenience, Table 1 provides a list of the abbreviations, symbols, and terms used along with their respective definitions.
  • TABLE 1
    LCD-TFT liquid-crystal display-thin-film transistor
    DRAM dynamic random-access memory
    FINFET fin-shaped field-effect transistor
    Bulk CMOS Bulk complementary metal-oxide-semiconductor
    FD-SOI fully depleted silicon-on-insulator
    FEOL front end of the line
    BEOL back end of the line
    TSV through silicon via
    OLED organic light-emitting diode
    RIE reactive ion etching
    CCP capacitively coupled plasma
    ICP inductively coupled plasma
    sccm standard cubic centimeters per minute
    slm standard liter per minute
    ONON silicon oxide and silicon nitride alternating layers
    OPOP silicon oxide and poly-silicon alternating layers
    TCAT terabit cell array transistor
    P-BICS pipe-shaped bit cost scalable
    QMS Quadrupole mass spectrometer
    ARC or BARC Anti-reflecting coating or Bottom anti-reflecting
    coating
    APF or a-C Amorphous carbon. Trademark of Applied Materials
    CAS chemical abstract service
    PCTFE Polychlorotrifluoroethene
    PVDF polyvinylidene fluoride
    PTFE Polytetrafluoroethylene
    SEM scanning electron microscope
    NAND Not AND or Negative-NAND or Negated AND
    TEOS Tetraethylorthosilicate
    LDTEOS low deposition rate TEOS
    BPSG Borophosphosilicateglass
    p-Si poly-silicon
    XPS X-ray photoelectron spectroscopy
    SiN Silicon nitride
    SiO Silicon oxide
    PECVD Plasma enhanced chemical vapor deposition
    LPCVD Low pressure chemical vapor deposition
  • As used herein, the indefinite article “a” or “an” means one or more.
  • As used herein, “about” or “around” or “approximately” in the text or in a claim means±10% of the value stated.
  • As used herein, “room temperature” in the text or in a claim means from approximately 20° C. to approximately 25° C.
  • The term “ambient temperature” refers to an environment temperature approximately 20° C. to approximately 25° C.
  • The term “substrate” refers to a material or materials on which a process is conducted. The substrate may refer to a wafer having a material or materials on which a process is conducted. The substrates may be any suitable wafer used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing. The substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step. For example, the wafers may include silicon layers (e.g., crystalline, amorphous, porous, etc.), silicon containing layers (e.g., SiO2, SiN, SiON, SiC, SiCN, SiOCN, SiCOH, etc.), metal containing layers (e.g., copper, cobalt, ruthenium, tungsten, manganese, platinum, palladium, nickel, ruthenium, gold, etc.) or combinations thereof. Furthermore, the substrate may be planar or patterned. The substrate may be an organic patterned photoresist film. The substrate may include layers of oxides which are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (for example, ZrO2 based materials, HfO2 based materials, TiO2 based materials, rare earth oxide based materials, ternary oxide based materials, etc.) or nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes. One of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may be a trench or a line. Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.
  • The term “wafer” or “patterned wafer” refers to a wafer having a stack of silicon-containing films on a substrate and a patterned hardmask layer on the stack of silicon-containing films formed for pattern etch.
  • The term “pattern etch” or “patterned etch” refers to etching a non-planar structure, such as a patterned mask layer on a stack of silicon-containing films.
  • As used herein, the term “etch” or “etching” means to use a plasma to remove material via ion bombardment, remote plasma, or chemical vapor reaction between the etching gas and substrate and refers to an isotropic etching process and/or an anisotropic etching process. The isotropic etch process involves a chemical reaction between the etching compound and the substrate resulting in part of material on the substrate being removed. This type of etching process includes chemical dry etching, vapor phase chemical etching, thermal dry etching, or the like. The isotropic etch process produces a lateral or horizontal etch profile in a substrate. The isotropic etch process produces recesses or horizontal recesses on a sidewall of a pre-formed aperture in a substrate. The anisotropic etch process involves a plasma etching process (i.e., a dry etch process) in which ion bombardment accelerates the chemical reaction in the vertical direction so that vertical sidewalls are formed along the edges of the masked features at right angles to the substrate (Manos and Flamm, Thermal etching an Introduction, Academic Press, Inc. 1989 pp. 12-13). The plasma etching process produces a vertical etch profile in a substrate. The plasma etching process produces vertical vias, apertures, trenches, channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the substrate.
  • The term “mask” refers to a layer that resists etching. The mask layer may be located above the layer to be etched. The mask layer also refers to a hardmask layer.
  • The term “etch stop” refers to a layer below the layer to be etched that protects layers underneath.
  • The term “device channel” refers to layers that are part of actual device and any damage to it will affect device performance.
  • The term “aspect ratio” refers to a ratio of the height of a trench (or via) to the width of the trench (or the diameter of the via).
  • The term “selectivity” means the ratio of the etch rate of one material to the etch rate of another material. The term “selective etch” or “selectively etch” means to etch one material more than another material, or in other words to have a greater or less than 1:1 etch selectivity between two materials.
  • The term “independently” when used in the context of describing R groups should be understood to denote that the subject R group is not only independently selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR1 x (NR2R3)(4-x), where M is an atom, x is 2 or 3, the two or three R1 groups may, but need not be identical to each other or to R2 or to R3. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.
  • Note that herein, the terms “film” and “layer” may be used interchangeably. It is understood that a film may correspond to, or related to a layer, and that the layer may refer to the film. Furthermore, one of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may range from as large as the entire wafer to as small as a trench or a line.
  • Note that herein, the terms “etching compound” and “etching gas” may be used interchangeably. It is understood that an etching compound may correspond to, or related to an etching gas, and that the etching gas may refer to the etching compound.
  • The terms “via”, “aperture”, “trench”, and “hole” are sometimes used interchangeably, and generally mean an opening in an interlayer insulator.
  • As used herein, the abbreviation “NAND” refers to a “Negated AND” or “Not AND” gate; the abbreviation “2D” refers to 2 dimensional gate structures on a planar substrate; the abbreviation “3D” refers to 3 dimensional or vertical gate structures, wherein the gate structures are stacked in the vertical direction.
  • The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviations (e.g., Si refers to silicon, N refers to nitrogen, O refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.).
  • The unique CAS registry numbers (i.e., “CAS”) assigned by the Chemical Abstract Service are provided to help better identify the molecules disclosed.
  • Please note that the silicon-containing films, such as silicon nitride and silicon oxide, are listed throughout the specification and claims without reference to their proper stoichiometry. The silicon-containing films may include pure silicon (Si) layers, such as crystalline Si, poly-silicon (p-Si or polycrystalline Si), or amorphous silicon; silicon nitride (SikNl) layers; or silicon oxide (SinOm) layers; or mixtures thereof, wherein k, l, m, and n, inclusively range from 0.1 to 6. Preferably, silicon nitride is SikNl, where k and l each range from 0.5 to 1.5. More preferably silicon nitride is Si3N4. Preferably silicon oxide is SinOm, where n ranges from 0.5 to 1.5 and m ranges from 1.5 to 3.5. More preferably, silicon oxide is SiO2. Herein, SiN and SiO in the following description are used to represent SikNl and SinOm containing layers, respectively. The silicon-containing film could also be a silicon oxide based dielectric material such as organic based or silicon oxide based low-k dielectric materials such as the Black Diamond II or III material by Applied Materials, Inc. with a formula of SiOCH. Silicon-containing film may also include SiaObCcNdHe where a, b, c, d, e range from 0.1 to 6. The silicon-containing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge.
  • Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
  • Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:
  • FIG. 1a is a cross-sectional side view of exemplary layers in a 3D NAND stack;
  • FIG. 1b is a cross-sectional side view of the exemplary layers in the 3D NAND stack showing polymer deposited on a sidewall during etching of the 3D NAND stack;
  • FIG. 1c is a cross-sectional side view of the exemplary layers in the 3D NAND stack showing particles generated during alternating SiO/SiN layer etching of a 3D NAND stack;
  • FIG. 1d is a cross-sectional side view of the exemplary layers in the 3D NAND stack showing selective etching of SiN exposed on the sidewall in the 3D NAND stack;
  • FIG. 2 is a cross-sectional side view of exemplary layers of a DRAM stack;
  • FIG. 3a is a cross-sectional side view of exemplary layers showing photoresist pattern over SiO insulation layer surrounding typical transistor device region to produce a transistor structure;
  • FIG. 3b is a cross-sectional side view of the exemplary layers of FIG. 3a after etching the SiO insulation layer;
  • FIG. 4 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C3F7I, O2 and Ar;
  • FIG. 5 is a graph demonstrating the electron impact ionization energy (eV) versus species concentration (Torr) of C3F7I;
  • FIG. 6 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C4F9I, O2 and Ar;
  • FIG. 7 is 1-C4F9I depth profile on a-C substrate;
  • FIG. 8 is 1-C4F9I depth profile on a-C(B) substrate;
  • FIG. 9 is 1-C4F9I depth profile on a-C(W) substrate;
  • FIG. 10 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with cC4F8; and
  • FIG. 11 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with C4F6.
    •  DESCRIPTION OF PREFERRED EMBODIMENTS
  • Disclosed are methods for plasma etching semiconductor structures, such as, channel holes, gate trenches, staircase contacts, capacitor holes, contact holes high aspect ratio structures, 3D NAND, slit trenches, self-aligned contact, self-aligned vias, super vias etc., in silicon-containing films. The disclosed methods include the steps of i) introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a silicon-containing film on a substrate, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4; and ii) introducing an inert gas into the reaction chamber; and iii) activating a plasma to produce an activated iodine-containing etching compound capable of etching the silicon-containing film from the substrate. Here the inert gas may be Ar, Kr, Xe, N2. He or Ne.
  • As shown in the examples that follow, the iodide ion in the disclosed iodine-containing etching compounds dissociates from the compounds at low energies (eV) (i.e., <20 eV). As a result, Applicants believe that the disclosed etching compounds may be used in dry plasma etch processes that produce less damage to the underlying substrates because they can be performed at lower plasma energies. For example, the disclosed iodine-containing etching compounds may be particularly suitable for low k etch processes in which damage is a particular concern because lower plasma energy may produce less damage to the porous low k material surrounding the etch site. The low damage to low k material may be due to the reduced generation of UV photons and F radicals given by iodine-containing etching compounds. The disclosed iodine-containing etching compounds may also prevent loss of the critical dimension and decrease low k surface roughness. In addition, molecules with two iodine atoms may enhance these benefits, although at a loss of volatility due to the size of the iodine atoms.
  • Iodine (10.5 eV) has a lower ionization threshold than Fluorine (17.4 eV) and the inert gases: Ar (15.8 eV), Xe (12.1 eV), and Kr (14 eV). Iodine may therefore be more easily ionized by the plasma than fluorine and iodine-containing etching compound may increase the plasma density. Iodine, being a heavy element (with a mass of 127 amu), may also behave similarly to the inert gases (such as Kr, with 88 amu, and Xe, with 131 amu) in the plasma and accelerate towards the wafer. During the etch of high aspect ratio structure, the energy of the ions gets weaker as they penetrate deeper, therefore many ions cannot reach the bottom of trench. However, Iodine ions being heavy may be accelerated toward the wafers by the voltage applied during the plasma etch process and penetrate deeply allowing to etch deep pattern structures with high aspect ratio. Fluorine's ionization threshold serves to maintain it as a neutral species. As a result, fluorine typically participates in the etching process via chemical reactions. Iodine exhibits less chemical reactivity than fluorine and is ionized and bombards the surface during the plasma etch process. The bond energy for C—I is also less than the bond energy for C—F, thereby causing the C—I bond to more easily break in the plasma compared to C—F bonds. Thus, iodine ions may easily be doped into a-C mask layer. Since iodine is a heavy element that makes it easier to implant and penetrate deeply in the mask layer than lighter elements. In addition, due to the weakness of the C—I bond and the fact that Iodine ionization threshold is low, the iodine containing etching compound have a low to negligible atmospheric lifetime making them good candidates to reduce the global warming potential caused by perfluorocarbon compounds.
  • The iodide ion dissociates from the disclosed etching compounds at low eVs (i.e., <20 eV), referring to the Comparative Example below. However, iodide ion implantation into the mask feature, such as the surface and/or the body/bulk is likely. This implantation may help to strengthen, minimize the damage, increase etch resistance of the mask feature and help it maintain its shape during the etching process. As shown in the examples that follow, after using the disclosed iodine-containing etch compound the composition of the pattern mask is modified. Applicants believe that the iodine ions modify the surface and incorporate into the bulk of the pattern mask layer by increasing the crosslinking with the organic mask layer (such as amorphous carbon mask). Due to the doping of the iodine ions and the crosslinking among carbon, iodine, hydrogen and fluorine atoms, and preferably between carbon and iodine, the density of the pattern mask layer increases, making the pattern mask layer stronger. In the examples that follow the strengthening effect and the etch resistance improvement due to the iodine ions have been proved by showing that the etching rate of the pattern mask layer is lower when etched by iodine-containing etching compound than when is etched by the traditional etching gases, such as cC4F8 and C4F6.
  • The disclosed iodine-containing etching compounds have the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, 1≤z≤4. When x=0, the disclosed iodine-containing etching compounds may not contain any hydrogen having the formula CnFyIz, wherein 4≤n≤10, 0≤y≤21, 1≤z≤4 and y+z≤2n+2. When n=4, the disclosed iodine-containing etching compounds have the formula C4FyIz, wherein 1≤z≤4, y≤10-z. Exemplary C4 iodine-containing etching compounds without containing H include C4F9I, C5F11I, C6F13I, C7F15I, C8F17I, C9F19I, C10F21I, C4F7I, C5F9I, C6F11I, C7F13I, C8F15I, C9F17I, C10F19I, C4F5I, C5F7I, C6F9I, C7F11I, C8F13I, C9F17I, C10F17I, C4F8I2, C5F10I2, C6F12I2, C7F14I2, C8F16I2, C9F18I2, C10F20I2, C4F6I2, C5F8I2, C6F10I2, C7F12I2, C8F14I2, C9F16I2, C10F18I2, C4F4I2, C5F6I2, C6F8I2, C7F10I2, C8F12I2, C9F14I2, C10F16I2, C4F7I3, C5F9I3, C6F11I3, CF13I3, C8F15I3, C9F17I3, C10F19I3, C4F4I3, C5F6I3, C6F8I3, C7F10I3, C8F12I3, C9F14I3, C10F16I3, C4F3I3, C5F5I3, C6F7I3, C7F9I3, C8F11I3, C9F13I3, C10F14I4, C4F6I4, C5F8I4, C6F10I4, C7F12I4, C8F14I4, C9F16I4, C10F18I4, C4F4I4, C5F6I4, C6F8I4, C7F10I4, C8F12I4, C9F14I4, C10F16I4, C4F2I4, C5F4I4, C6F6I4, C7F8I4, C8F10I4, C9F12I4, C10F14I4, and their isomers.
  • Exemplary disclosed iodine-containing etching compounds without containing H having a general formula: CnF2n+1I, where 4≤n≤10, are listed in Table 2. These molecules are commercially available or may be synthesized by methods known in the art. Their structure formula, CAS numbers and boiling points are included in Table 2. The disclosed iodine-containing etching compounds without containing H having a general formula: CnF2n+1I, where 4≤n≤10, may also include their isomers.
  • TABLE 2
    Etching
    compounds Formula Structure CAS number Boiling point (° C.)
    Perfluorobutyl iodide 1-C4F9I
    Figure US20210407817A1-20211230-C00001
         		423-39-2 67.0° C.
    Perfluoropentyl Iodide 1-C5F11I
    Figure US20210407817A1-20211230-C00002
         		638-79-9 94.4° C.
    Perfluorohexyl iodide 1-C6F13I
    Figure US20210407817A1-20211230-C00003
         		355-43-1 115-117° C. @ 1 mmHg
    Perfluoroheptyl Iodide 1-C7F15I
    Figure US20210407817A1-20211230-C00004
         		355-58-0 137-138° C.
    Perfluorooctyl iodide 1-C8F17I
    Figure US20210407817A1-20211230-C00005
         		507-63-1 160-161° C.
    Perfluorononyl iodide 1-C9F19I
    Figure US20210407817A1-20211230-C00006
         		558-97-4  181° C.
    Perfluorodecyl iodide 1-C10F21I
    Figure US20210407817A1-20211230-C00007
         		423-62-1 112-115° C. @ 50 mmHg
  • The disclosed iodine-containing etching compounds are suitable for etching silicon-containing films that include a layer of silicon oxide (SiO), silicon nitride (SiN), pure silicon (Si) such as crystalline Si, poly-silicon (p-Si or polycrystalline Si), or amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON, SiaObHcCdNe, where a>0; b, c, d and e≥0, or combinations thereof. The silicon-containing film may also include alternating SiO and SiN (ONON) layers or SiO and p-Si (OPOP) layers. The silicon-containing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge.
  • The etch rate of SiN may be enhanced while maintaining high selectivity to the mask layer when the disclosed iodine-containing etching compounds include H, but are not limited to. The disclosed Iodine-containing etching compounds having one H when x=1 have the formula CnHFyIz, wherein 4≤n≤10, 0≤y≤20, 1≤z≤4, and y+z≤2n+1. Exemplary compounds include C4HF8I, C5HF10I, C6HF12I, C7HF14I, C8HF16I, C9HF18I, C10HF20I, C4HF6I, C5HF8I, C6HF10I, C7HF12I, C8HF14I, C9HF16I, C10HF18I, C4HF4I, C5HF6I, C6HF8I, C7HF10I, C8HF12I, C9HF14I, C10HF16I, C4HF7I2, C5HF9I2, C6HF11I2, C7HF13I2, C8HF15I2, C9HF17I2, C10HF19I2, C4HF5I2, C5HF7I2, C6HF9I2, C7HF11I2, C8HF13I2, C9HF15I2, C10HF17I2, C4HF3I2, C5HF5I2, C6HF7I2, C7HF9I2, C8HF11I2, C9HF13I2, C10HF15I2, C4HF6I3, C5HF8I3, C6HF10I3, C7HF12I3, C8HF14I3, C9HF16I3, C10HF18I3, C4HF4I3, C5HF6I3, C6HF8I3, C7HF10I3, C8HF12I3, C9HF14I3, C10HF16I3, C4HF5I4, C5HF7I4, C6HF9I4, C7HF11I4, C8HF13I4, C9HF15I4, C10HF17I4, C4HF3I4, C5HF5I4, C6HF7I4, C7HF9I4, C8HF11I4, C9HF13I4, C10HF15I4, C4HFI4, C5HF3I4, C6HF5I4, C7HF7I4, C8HF9I4, C9HF11I4, C10HF13I4 and their isomers.
  • The disclosed Iodine-containing etching compounds having two hydrogens when x=2 have the formula CnH2FyIz, wherein 4≤n≤10, 0≤y≤19, 1≤z≤4, and y+z≤2n. Exemplary compounds include C4H2F7I, C5H2F9I, C6H2F11I, C7H2F13I, C8H2F15I, C9H2F17I, C10H2F19I, C4H2F5I, C5H2F7I, C6H2F9I, C7H2F11I, C8H2F13I, C9H2F15I, C10H2F17I, C4H2F6I2, C5H2F8I2, C6H2F10I2, C7H2F12I2, C8H2F14I2, C9H2F16I2, C10H2F11I2, C4H2F4I2, C5H2F6I2, C6H2F8I2, C7H2F10I2, C8H2F12I2, C9H2F14I2, C10H2F16I2, C4H2F5I3, C5H2F7I3, C6H2F9I3, C7H2F11I3, C8H2F13I3, C9H2F15I3, C10H2F17I3, C4H2F3I3, C5H2F5I3, C6H2F7I3, C7H2F9I3, C8H2F11I3, C9H2F13I3, C10H2F15I3, C4H2F4I4, C5H2F6I4, C6H2F8I4, C7H2F10I4, C8H2F12I4, C9H2F14I4, C10H2F16I4, C4H2F2I4, C5H2F4I4, C6H2F6I4, C7H2F8I4, C8H2F10I4, C9H2F12I4, C10H2F14I4 and their isomers.
  • The disclosed Iodine-containing etching compounds having three hydrogens when x=3 have the formula CnH3Fy1z, wherein 4≤n≤10, 0≤y≤18, 1≤z≤4, and y+z≤2n−1. Exemplary compounds include C4H3F6I, C5H3F8I, C6H3F10I, C7H3F12I, C8H3F14I, C9H3F16I, C10H3F16I, C4H3F4I, C5H3F6, C6H3F8I, C7H3F10I, C8H3F12I, C9H3F14I, C10H3F16I, C4H3F5I2, C5H3F7I2, C6H3F9I2, C7H3F11I2, C8H3F13I2, C9HF15I2, C10H3F17I2, C4H3F3I2, C5H3F5I2, C6H3F7I2, C7H3F9I2, C8H3F11I2, C9H3F13I2, C10H3F15I2, C4H3F4I3, C8H3F6I3, C6H3F8I3, C7H3F10I3, C8H3F12I3, C9H3F14I3, C10H3F16I3, C4H3F2I3, C5H3F4I3, C6H3F6I3, C7H3F8I3, C8H3F10I3, C9H3F12I3, C10H3F14I3, C4H3F3I4, C5H3F5I4, C6H3F7I4, C7H3F9I4, C8H3F11I4, C9H3F13I4, C10H3F15I4. C4H3F1I4, C5H3F3I4, C6H3F5I4, C7H3F7I4, C8H3F9I4, C9H3F11I4, C10H3F13I4 and their isomers.
  • The disclosed Iodine-containing etching compounds having four hydrogens when x=4 have the formula CnH4FyIz, wherein 4≤n≤10, 0≤y≤17, 1≤z≤4, and y+z≤2n−2. Exemplary compounds include C4HF5I, C5H4F7I, C6H4F9I, C7H4F11I, C8H4F13I, C9H4F15I, C10H4F17I, C4H4F3I, C5H4F5I, C6H4F7I, C7H4F9I, C8H4F11I, C9H4F13I, C10H4F15I, C4H4F4I2, C5H4F6I2, C6H4F8I2, C7H4F10I2, C8H4F12I2, C9H4F14I2, C10H4F16I2, C4H4F2I2, C5H4F4I2, C6H4F6I2, C7H4F8I2, C8H4F10I2, C9H4F12I2, C10H4F14I2, C4H4F3I3, C5H4F5I3, C6H4F7I3, C7H4F9I3, C8H4F11I3, C9H4F13I3, C10H4F15I3, C4H4FI3, C5H4F3I3, C6H4F5I3, C7H4F7I3, C8H4F9I3, C9H4F11I3, C10H4F13I3, C4H4F2I4, C5H4F4I4, C6H4F6I4, C7H4F8I4, C8H4F10I4, C9H4F12I4, C10H4F14I4, C4H4I4, C5H4F2I4, C6H4F4I4, C7H4F6I4, C8H4F8I4, C9H4F10I4, C10H4F12I4 and their isomers.
  • Applicants believe that the molecules having 4 or more than 4 carbon atoms may provide better etch rate and sidewall protection, e.g., straight profile, no bowing, no tapering, no twisting, no incomplete etch, no variation of critical dimension from top to bottom of the structure etched, during the etching process than less than 4 carbon molecules. Applicants believe that the molecules having 4 or more than 4 carbon atoms may also provide a straighter profile, without bowing, tapering, twisting and incomplete etch, or variation of critical dimension from top to bottom of the structure etched than less than 4 carbon molecules. For sidewall protection, the carbon 24 molecules are preferred because Applicants believe they will produce thicker passivation layers.
  • The disclosed iodine-containing etching compounds may provide high selectivity to mask layers, photoresist, etch stop layers and device channel materials and no profile distortion in high aspect ratio structures (HAR), such as those having an aspect ratio ranging from 1:1 to 200:1 such as DRAM and 3D NAND structures. Alternatively, the disclosed iodine-containing etching compounds may also provide high selectivity to mask layers or silicon-containing film, such as those having an aspect ratio ranging from 1:1 to 200:1 in contact etch applications.
  • The disclosed iodine-containing etching compounds may provide infinite selectivity for wide process conditions of etching. Herein the selectivity refers to the etching rate ratio of two different layers. For example, the selectivity for SiO layer vs. a-C layer is the etch rate of the SiO divided by the etching rate of the a-C layer. The disclosed iodine-containing etching compounds may provide improved selectivity between the silicon-containing films and mask materials, less damage to channel region, improved critical dimension uniformity and reduced profile distortion such as bowing, twisting, tapering, notching, under-cut, maintain the same critical dimension from top to bottom of the etch structure and arcing in pattern high aspect ratio structures. The disclosed iodine-containing etching compounds may also etch through alternating layers of p-Si, SiO, and/or SiN, resulting in a vertical etch profile. (i.e., demonstrating selectivity ranging from 2:1 to 1:2 between the alternating layers). The disclosed iodine-containing etching compound plasma etches the alternating SiO and SiN (ONON) layers having a selectivity between approximately 1:2 to approximately 2:1 with respect to the SiO layer versus SiN layer. Preferably, the disclosed iodine-containing etching compound plasma etches the alternating SiO and SiN (ONON) layers having a selectivity of approximately 1:1 with respect to the SiO layer versus SiN layer.
  • The disclosed iodine-containing etching compounds are provided at greater than 95% v/v purity, preferably at greater than 99.99% v/v purity, and more preferably at greater than 99.999% v/v purity. The disclosed iodine-containing etching compounds contain less than 5% by volume trace gas impurities, with less than 150 ppm by volume of impurity gases, such as N2 and/or H2O and/or CO2, contained in said trace gaseous impurities. Preferably, the water content in the plasma etching gas is less than 20 ppm by weight. The purified product may be produced by distillation and/or passing the gas or liquid through a suitable adsorbent, such as a 4 Å molecular sieve.
  • The disclosed iodine-containing etching compounds contain less than 10% v/v, preferably less than 1% v/v, more preferably less than 0.1% v/v, and even more preferably less than 0.01% v/v of any of its isomers, which may be purified by distillation of the gas or liquid to remove isomers and may provide better process repeatability.
  • Alternatively, the disclosed iodine-containing etching compounds may contain between 0.01% v/v and 99.99% v/v of its isomers, particularly when the isomer mixture provides improved process parameters or if isolation of the target isomer is too difficult or expensive. For example, the disclosed iodine-containing etching compounds may comprise between approximately 50% v/v and approximately 75% v/v 1-Iodononafluorobutane and between approximately 25% v/v and approximately 50% v/v 2-Iodononafluorobutane and between approximately 25% v/v and approximately 50% v/v Iodononafluoro-t-butane. The mixture of isomers may also reduce the need for two or more gas lines to the reaction chamber.
  • Some of the disclosed iodine-containing etching compounds are gaseous at room temperature and atmospheric pressure. For the non-gaseous (i.e., liquid or solid) compounds, their gas form may be produced by vaporizing the compounds through a conventional vaporization step, such as direct vaporization or by bubbling with inert gas (such as N2, Ar, He). The non-gaseous compounds may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into a reactor.
  • The disclosed iodine-containing etching compounds are suitable for plasma etching semiconductor structures, such as, channel holes, gate trenches, staircase contacts, slits, capacitor holes, contact holes, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films. The disclosed iodine-containing etching compounds are not only compatible with currently available mask materials but also compatible with the future generations of mask materials because the disclosed iodine-containing etching compounds induce little to no damage on the mask along with good profile of high aspect ratio structures. In other words, the disclosed iodine-containing etching compounds may produce vertical etched patterns having minimal to no bowing, pattern collapse, or roughness. In order to achieve these properties, the disclosed iodine-containing etching compounds may deposit an etch-resistant polymer layer during etching to help reduce the direct impact of the oxygen and fluorine radicals during the etching process. The disclosed iodine-containing etching compounds may also reduce damage to p-Si or crystalline Si channel structure during etching.
  • The disclosed iodine-containing etching compounds selectively etch the silicon-containing layers from a buried landing layer or material which is a metal layer located at the bottom of the structure to be etched in most applications. The disclosed iodine-containing etching compounds do not etch metal landing layers. The buried landing layer may be an etching stop layer or a diffusion barrier layer. Materials of the metal landing layers may be a tungsten metal worldline in a 3D NAND structure and/or another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof and/or etch stop layers such as metals or metal oxides or nitrides layer such as AlO, WO, HfO, TiO, TaO, InO, CrO, RuO, CoO, MoO, ZrO, SnO TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN, ZrN, SnN or combination thereof etc. The disclosed iodine-containing etching compounds induce little to no damage to the material at bottom of the contact hole, staircase and slit (such as tungsten metal world line in a 3D NAND structure and/or other metals such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof etc.) and/or etch stop layers such as metals or metal oxides or nitrides layer (AlO, WO, HfO, TiO, TaO, InO, CrO, RuO, CoO, MoO, ZrO, SnO TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN, ZrN, SnN or combination thereof etc.). One of ordinary skill in the art will recognize that a barrier layer can also be composed of a combination of the previously mentioned metals and metals oxide and nitride, such a barrier layer being Ti/TiN, Ti/TiN/Ti, TiZrN, Ta/TaN, TaN/Cu/TaN, TaN/Ru/TaN etc. A barrier might also contained silicide (such as TiSiN, TaSiN, TiSi2, MnSiO, etc.), phosphide (such as CuWP, NiMoP, NiP etc.), carbide (such as TaC, TaCN, WCN etc.), boride (such as NiMoB, NiB etc.) or combination thereof. Preferably, the disclosed iodine-containing etching compounds are suitably volatile and stable during the etching process for delivery into the reactor/chamber.
  • Material compatibility tests are important to determine if any of the disclosed iodine-containing etching compounds will react with chamber materials and degrade the performance of the chamber with short term or long term use. Key materials involved in parts of the chamber, valves, etc. include stainless steel, aluminum, nickel, PCTFE, PVDF, PTFE, PFA, PP, kalrez, viton and other metals and polymers. At times these materials are exposed to high temperatures, for example, higher than 20° C., and high pressures, for example, higher than 1 atm, which may enhance their degradation. The metrology methods may include visual inspection, weight measurement, measuring nanometer scale changes in scanning electron microscopy (SEM), tensile strength, hardness, etc.
  • The disclosed iodine-containing etching compounds may be used to plasma etch silicon-containing films on a substrate. The disclosed plasma etching method may be useful in the manufacture of semiconductor devices such as NAND or 3D NAND gates or Flash or DRAM memory or transistors such as fin-shaped field-effect transistor (FinFET), Gate All Around (GAA)-FET, Nanowire-FET, Nanosheet-FET, Forksheet-FET, Complementary FET (CFET), Bulk complementary metal-oxide-semiconductor (Bulk CMOS), MOSFET, fully depleted silicon-on-insulator (FD-SOI) structures. The disclosed iodine-containing etching compounds may be used in other areas of applications, such as different front end of the line (FEOL) and back end of the line (BEOL) etch applications. Additionally, the disclosed iodine-containing etching compounds may also be used for etching Si in 3D through silicon via (TSV) etch applications for interconnecting memory to logic on a substrate and in MEMS applications.
  • The plasma etching method includes providing a reaction chamber having a substrate disposed therein. The reaction chamber may be any enclosure or chamber within a device in which etching methods take place such as, and without limitation, reactive ion etching (RIE), capacitively coupled plasma (CCP) with single or multiple frequency RF sources, inductively coupled plasma (ICP), or microwave plasma reactors, or other types of etching systems capable of selectively removing a portion of the silicon-containing film or generating active species. One of ordinary skill in the art will recognize that the different plasma reaction chamber designs provide different electron temperature control. Suitable commercially available plasma reaction chambers include but are not limited to the Applied Materials magnetically enhanced reactive ion etcher sold under the trademark eMAX™ or the Lam Research Dual CCP reactive ion etcher dielectric etch product family sold under the trademark 2300® Flex™. The RF power in such may be pulsed to control plasma properties and thereby improving the etch performance (selectivity and damage) further.
  • Alternatively, the plasma-treated reactant may be produced outside of the reaction chamber. The MKS Instruments' ASTRONi® reactive gas generator may be used to treat the reactant prior to passage into the reaction chamber. Operated at 2.45 GHz, 7 kW plasma power, and a pressure ranging from approximately 0.5 Torr to approximately 10 Torr, the reactant O2 may be decomposed into two 0 radicals. Preferably, the remote plasma may be generated with a power ranging from about 1 kW to about 10 kW, more preferably from about 2.5 kW to about 7.5 kW.
  • The reaction chamber may contain one or more than one substrate. For example, the reaction chamber may contain from 1 to 200 silicon wafers having from 25.4 mm to 450 mm diameters. The substrates may be any suitable substrates used in semiconductor, photovoltaic, flat panel or LCD-TFT device manufacturing. Examples of suitable substrates include wafers, such as silicon, silica, glass, Ge, SiGe, GeSn, InGaAs, GaSb, InP, or GaAs wafers. The wafer will have multiple films or layers on it from previous manufacturing steps, including silicon-containing films or layers. The layers may or may not be patterned. Examples of suitable layers include without limitation silicon (such as amorphous silicon, p-Si, crystalline silicon, any of which may further be p-doped or n-doped with B, C, P, As, Ga, In, Sn, Sb, Bi and/or Ge), silica, silicon nitride, silicon oxide, silicon oxynitride, SiaObHcCdNe, (wherein a>0; b, c, d, e≥0), Ge, SiGe, GeSn, InGaAs, GaSb, InP; mask layer materials such as amorphous carbon with or without dopants, antireflective coatings, photoresist materials, a metal oxide, such as AlO, TiO, HfO, ZrO, SnO, TaO etc. or a metal nitride layer such as AlN, ZrN, SnN, HfN, titanium nitride, tantalum nitride etc. or combinations thereof; etch stop layer materials such as silicon nitride, polysilicon, crystalline silicon, silicon carbide, SiON, SiCN or combinations thereof, device channel materials such crystalline silicon, epitaxial silicon, doped silicon, SiaObHcCdNe, (wherein a>0; b, c, d, e≥0) or combinations thereof. The silicon oxide layer may form a dielectric material, such as an organic based or silicon oxide based low-k dielectric material (e.g., a porous SiCOH film). An exemplary low-k dielectric material is sold by Applied Materials under the trade name Black Diamond II or III. Additionally, layers comprising tungsten or noble metals (e.g. platinum, palladium, rhodium or gold) may be used. Furthermore, examples of the silicon-containing films may be SiaObHcCdNe, (wherein a>0; b, c, d, e≥0). Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.
  • The following are exemplary embodiments of the substrates on which the disclosed iodine-containing etching compounds may be applied to etch.
  • In one embodiment, a substrate 100 may include a stack of multiple layers as shown in FIG. 1a . FIG. 1a is a cross-sectional side view of exemplary layers in a 3D NAND stack to produce a 3D NAND gate. In FIG. 1a , a stack of seven alternative SiO/SiN (i.e., 104 a/104 b) layers 104 is located on top of a silicon wafer 102 (i.e., ONON or TCAT technology). In some applications, the wafer 102 may be a buried landing layer or material, such as tungsten metal worldline in a 3D NAND structure and/or another metal such as W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Pd, Ir, Nb, Cr, Rh, V, Au, Ag or combination thereof etc. and/or etch stop or diffusion barrier layers such as metals or metal oxides or nitrides layer (AlO, WO, HfO, TiO, TaO, InO, WO, CrO, RuO, CoO, MoO, TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN or combination thereof etc.). One of ordinary skill in the art will recognize that a barrier layer can also be composed of a combination of the previously mentioned metals and metals oxide and nitride, such a barrier layer being Ti/TiN, Ti/TiN/Ti, TiZrN, Ta/TaN, TaN/Cu/TaN, TaN/Ru/TaN etc. A barrier might also contained silicide (such as TiSiN, TaSiN, TiSi2. MnSiO, etc.), phosphide (such as CuWP, NiMoP, NiP etc.), carbide (such as TaC, TaCN, WCN etc.), boride (such as NiMoB, NiB etc.) or combination thereof. One of ordinary skill in the art will recognize that some technologies replace the SiN layers 104 b with p-Si layers (e.g., SiO/p-Si or P-BICS technology). A hardmask layer 106 is located on the top of the seven SiO/SiN layers 104. The hardmask layer 106 may be an amorphous carbon (a-C) hardmask layer with or without dopants. The hardmask layer 106 may be a layer of CVD, PECVD, ALD, PEALD or spin on deposited (SOD) amorphous carbon or doped amorphous carbon, silicon-containing spin on mask, or carbon-containing spin on mask. The hardmask layer 106 may contain C and H, as well as other elements, such as boron, nitrogen, sulfur, chlorine, fluorine or metals (Al, Zr, Ti, W, Y) etc., to improve etch resistance during SiO/SiN layer etch. In this case, the hardmask layer 106 is a doped a-C layer, for example, a boron-doped a-C layer, a tungsten-doped a-C layer, etc. An antireflective coating layer 108 is located on top of the hardmask layer 106. A patterned photoresist layer 110 is located on top of the antireflective coating layer 108. Herein, a SiON layer (not shown) may be present between the antireflective coating layer 108 and the hardmask layer 106 to transfer the pattern in photoresist layer 110 to the hardmask layer 106 to form a patterned hardmask layer. One of ordinary skill in the art will recognize that the stack of layers in the substrate 100 in FIG. 1a is provided for exemplary purposes only and that the disclosed iodine-containing etching compounds may be used to etch other types of stacks of layers. Furthermore, one of ordinary skill in the art will recognize that the number alternating SiO/SiN or SiO/p-Si layers 104 in the stack of the substrate 100 may vary (i.e., may include more or less than the seven SiO/SiN (104 a/104 b) layers depicted).
  • FIG. 1b is a cross-sectional side view of the exemplary layers in the 3D NAND stack of FIG. 1a showing polymer deposited on a sidewall by etching. The disclosed iodine-containing etching compounds may produce fragments during the plasma process that are suitable for both anisotropically etching the silicon-containing films 104 and depositing an I-containing polymer passivation layer 212 on sidewalls of a structure being etched as shown in FIG. 1b . The difference between FIG. 1b and FIG. 1a is in FIG. 1b via 214 is formed in substrate 100 by plasma etching using the disclosed iodine-containing etch compounds, which also deposit the polymer passivation layer 212 on the sidewalls of the via 214. The polymer passivation layer 212 also provides smoother sidewall, less bowing and less deformation at the bottom of the via 214. The polymer passivation layer 212 may however be easily removed or cleaned by dry or wet etch chemistries known in the art.
  • FIG. 1c is a cross-sectional side view of the exemplary layers in the 3D NAND stack of FIG. 1a showing particles 316 generated during alternating SiO/SiN layer etching in a 3D NAND stack. The particles 316 generated on the sidewalls of the alternative SiO/SiN (i.e., 104 a/104 b) layers 104 as shown in FIG. 1c may be minimized by using the disclosed iodine-containing etching compounds. The difference between FIG. 1c and FIG. 1b is in FIG. 1c the alternative SiO/SiN exposed sidewall has particles 316 generated during plasma etching. Applicants do not believe that the disclosed iodine-containing etching compounds will generate the particles 316 shown in FIG. 1 c.
  • FIG. 1d is a cross-sectional side view of the exemplary layers in the 3D NAND stack of FIG. 1a showing selective isotropic etching of the SiN layers 104 b exposed on the sidewall in the 3D NAND stack after the anisotropic etching process. The SiN exposed sidewall in stack 100 may be etched selectively as shown in FIG. 1d by using the disclosed iodine-containing etching compounds to selectively break the Si—N bonds in the SiN layers 104 b over the Si—O bond in the SiO layers 104 a forming a selective sidewall SiN etch 418 on the stack of SiO/SiN layers 104 in the via 214. The difference between FIG. 1d and FIG. 1b is in FIG. 1d SiN exposed on the alternative SiO/SiN sidewall is selectively etched by the disclosed iodine-containing etching compounds forming the selective sidewall SiN etch 418. Typically, the selective sidewall SiN etch 418 is performed by wet etching using mixtures with phosphoric acid. Replacing wet etch process with dry plasma etch processes is known to greatly improve the economics of semiconductor device fabrication process since wet etching requires moving the substrate to different wet etching equipment. With the disclosed methods, all etching, including the selective sidewall SiN etch of FIG. 1d , may be performed in one piece of etching equipment, which may reduce the cost of the semiconductor fabrication.
  • In alternative embodiment, substrate 100 may include a stack of multiple layers thereon as shown in FIG. 2. FIG. 2 is a cross-sectional side view of exemplary layers in a DRAM stack to produce a DRAM memory. In FIG. 2, a stack of four layers is located on top of a silicon wafer 102. A hardmask layer 106 is located on top of a large SiO layer 104 a. An antireflective coating layer 108 is located on top of the hardmask layer 106. A pattern photoresist layer 110 is located on top of the antireflective coating 108. A SiON layer (not shown) may be present between the antireflective coating layer 108 and the hardmask layer 106 to transfer pattern in photoresist layer 110 to the hardmask layer 106. One of ordinary skill in the art will recognize that the stack of layers in FIG. 2 is provided for exemplary purposes only and that the disclosed iodine-containing etching compounds may be used to etch other stacks of layers, for example, for a stack where the hardmask layer 106 is replaced with a TiN layer. Furthermore, one of ordinary skill in the art will recognize that the number of layers in the stack may vary (i.e., may include more or less than the layers depicted).
  • FIG. 3a is a cross-sectional side view of exemplary layers showing photoresist pattern over SiO insulation layer surrounding a typical transistor device region to produce a transistor structure. Substrate 600 may include a stack of four layers surrounding a transistor gate electrode region supported on the Silicon wafer 602 as shown in FIG. 3a . The transistor region shown in FIG. 3a includes two doped silicon regions 606 acting as source and drain. Transistor gate dielectric 614 is present underneath gate electrode 616. The whole transistor, i.e., transistor gate dielectric 614 and gate electrode 616, is surrounded by a thin SiN layer 608 which may later act as etch stop layer during contact etch. Each transistor device region 616/606 is separated by SiO isolation regions 604 in the silicon wafer 602 to minimize electrical interference. One of ordinary skill in the art will recognize that layer 602 may be located on top of a silicon oxide layer of the Silicon on Insulator (SOI) wafer. Another SiO layer 610 is deposited on the transistor and used to insulate any metal contact to the transistor device regions 606. Photoresist mask 612 is used to pattern the SiO layer 610. Etching is performed using the disclosed iodine-containing etching compounds in plasma environment. The photoresist mask 612 serves as a template to etch the SiO layer 610 and etching is stopped on the SiN layer 608 as shown in FIG. 3 b.
  • FIG. 3b is a cross-sectional side view of the exemplary layers of FIG. 3a after etching the SiO insulation layer. The difference between FIG. 3b and FIG. 3a is in FIG. 3b vias 718 are formed in the SiO layer 610 through etching by the disclosed iodine-containing etching compounds. The SiO layer 610 may be etched with photoresist layer 612 as a mask layer. The mask layer may be any suitable photoresist mask materials, such as TiN, a-C and so on. The etching may be stopped at the underlying SiN layer 608.
  • The disclosed iodine-containing etching compounds may also be used to etch the SiN layer 608 with different plasma conditions and different mixtures. One of ordinary skill in the art will recognize that the stack and geometry of layers in FIG. 3a and FIG. 3b is provided for exemplary purposes only and that the disclosed iodine-containing etching compounds may be used to etch other types of stacks of layers. Furthermore, one of ordinary skill in the art will recognize that the number of layers in the stack may vary (i.e., may include more or less than the four layers depicted).
  • The vapor of the disclosed iodine-containing etching compounds is introduced into the reaction chamber containing the substrate and silicon-containing films. The vapor may be introduced to the chamber at a flow rate ranging from approximately 0.1 sccm to approximately 1 slm. For example, for a 200 mm wafer size, the vapor may be introduced to the chamber at a flow rate ranging from approximately 5 sccm to approximately 50 sccm. Alternatively, for a 450 mm wafer size, the vapor may be introduced to the chamber at a flow rate ranging from approximately 25 sccm to approximately 250 sccm. One of ordinary skill in the art will recognize that the flow rate may vary from tool to tool.
  • The disclosed iodine-containing etching compounds may be supplied either in neat form or in a blend with an inert gas, such as N2, Ar, Kr, Ne He, Xe, etc., or solvent. The disclosed iodine-containing etching compounds may be present in varying concentrations in the blend. For liquid iodine-containing etching compounds, the vapor form of the iodine-containing etching compounds may be produced by vaporizing the neat or blended iodine-containing etching compound solution through a conventional vaporization step such as direct vaporization or by bubbling. The neat or blended iodine-containing etching compounds may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into the reactor.
  • Alternatively, the neat or blended iodine-containing etching compounds may be vaporized by passing a carrier gas into a container containing the disclosed iodine-containing etching compounds or by bubbling the carrier gas into the disclosed iodine-containing etching compounds. The carrier gas may include, but is not limited to, Ar, He, N2, Kr, Xe, Ne and mixtures thereof. Bubbling with a carrier gas may also remove any dissolved oxygen present in the neat or blended iodine-containing etching compound solution The carrier gas and disclosed iodine-containing etching compounds are then introduced into the reactor as a vapor.
  • If necessary, the container containing the disclosed iodine-containing etching compounds may be heated to a temperature that permits the iodine-containing etching compounds to be in liquid phase and to have a sufficient vapor pressure for delivery into an etching tool. The container may be maintained at temperatures in the range of, for example, approximately 0° C. to approximately 150° C., preferably from approximately 25° C. to approximately 100° C., more preferably from approximately 25° C. to approximately 50° C. More preferably, the container is maintained at room temperature (approximately 25° C.) in order to avoid heating lines to the etch tool. Those skilled in the art recognize that the temperature of the container may be adjusted in a known manner to control the amount of iodine-containing etching compound vaporized.
  • Additionally, the iodine-containing etching compounds are delivered in purity ranging from 95% to 99.999% by volume and may be purified with known standard purification techniques for removal of CO, CO2, N2, H2O, HF, H2S, SO2, halides, and other hydrocarbons or hydrohalocarbons.
  • An inert gas is also introduced into the reaction chamber in order to sustain the plasma. The inert gas may be He, Ar, Xe, Kr, Ne, N2, He or combinations thereof. The etching gas and the inert gas may be mixed prior to introduction to the chamber, with the inert gas comprising between approximately 0.01% v/v and approximately 99.9% v/v of the resulting mixture. Alternatively, the inert gas may be introduced to the chamber continuously while the etching gas is introduced to the chamber in pulses.
  • The vapor of the disclosed etching gas and inert gas are activated by plasma to produce an activated etching gas. The plasma decomposes the etching gas into radical form (i.e., the activated etching gas). The plasma may be generated by applying RF or DC power. The plasma may be generated with a RF power ranging from about 25 W to about 100,000 W. The plasma may be generated remotely or within the reactor itself. The plasma may be generated in dual CCP or ICP mode with RF applied at both electrodes. RF frequency of plasma may range from 100 KHz to 1 GHz. Different RF sources at different frequency may be coupled and applied at same electrode. Plasma RF pulsing may be further used to control molecule fragmentation and reaction at substrate. One of skill in the art will recognize methods and apparatus suitable for such plasma treatment.
  • A quadrupole mass spectrometer (QMS), optical emission spectrometer, FTIR, or other radical/ion measurement tools may measure the activated etching gas from the chamber exhaust to determine the types and numbers of species produced. If necessary, the flow rate of the etching gas and/or the inert gas may be adjusted to increase or decrease the number of radical species produced.
  • The disclosed etching gases may be mixed with other gases either prior to introduction into the reaction chamber or inside the reaction chamber. Preferably, the gases may be mixed prior to introduction to the chamber in order to provide a uniform concentration of the entering gas.
  • In another alternative, the vapor of the iodine-containing etching compound may be introduced into the chamber independently of the other gases, such as when two or more of the gases react or are easier to deliver independently.
  • In another alternative, the etching gas and the inert gas are the only two gases that are used during the etching process.
  • Exemplary other gases include, without limitation, oxidizers such as O2, O3, CO, CO2, NO, N2O, NO2, H2O, H2O2, COS, SO2 and combinations thereof. The disclosed etching gases and the oxidizer may be mixed together prior to introduction into the reaction chamber.
  • Alternatively, the oxidizer may be introduced continuously into the chamber and the etching gas introduced into the chamber in pulses. The oxidizer may comprise between approximately 0.01% v/v to approximately 99.99% v/v of the mixture introduced into the chamber (with 99.99% v/v representing introduction of almost pure oxidizer for the continuous introduction alternative).
  • Other exemplary gases with which the disclosed iodine-containing etching compounds may be used include additional etching gases, such as cC4F8, C4F8, cC5F8, C5F8, C4F6, CF4, CH3F, CF3H, CH2F2, C3HF7, C3F6, C3H2F6, C3H2F4, C3H2F5, C4HF7. C5HF9, C3F6, C3F8, CF3I, C2F3I, C2F5I, C3F7I, 1-lodoheptafluoropropane (1-C3F7I), 2-lodoheptafluoropropane (2-C3F7I), C3HF7, COS, FNO, F—C≡N, CS2, SO2, SF6, trans-1,1,1,4,4,4-hexafluoro-2-butene (trans-C4H2F6), cis-1,1,1,4,4,4-hexafluoro-2-butene (cis-C4H2F6), hexafluoroisobutene (C4H2F6), trans-1,1,2,2,3,4-hexafluorocyclobutane (trans-C4H2F6), 1,1,2,2,3-pentafluorocyclobutane (C4H3F5), 1,1,2,2-tetrafluorocyclobutane (C4H4F4), and cis-1,1,2,2,3,4-hexafluorocyclobutane (cis-C4H2F6) or combination thereof. For example, approximately 1% v/v to approximately 25% v/v of the disclosed iodine-containing etching compound may be used with a balance of C4F6 or cC4F8. As shown in the examples that follow, the combination of the disclosed iodine-containing etching compounds with conventional etch gases may result in increased etch rates while maintaining the higher selectivity between the substrate and layer to be etched associated with the disclosed iodine-containing etching compounds.
  • The vapor of the disclosed iodine-containing etching compounds and the etching gas may be mixed prior to introduction to the reaction chamber. The additional etching gas may comprise between approximately 0.01% v/v to approximately 99.99% v/v of the mixture introduced into the chamber.
  • In one non-limiting exemplary plasma etch process, the vapor of a disclosed iodine-containing compound, such as C4F9I, is introduced into a 200 mm Dual CCP plasma etch tool using a controlled gas flow device. The controlled gas flow device may be a mass flow controller or a bubbler design with inert gas flow to deliver the vapor of the desired molecule. In case of high boiling point molecules, a special low pressure drop mass flow controller from Brooks Automation (No. GF120XSD), MKS Instruments, etc., may be used. The pressure of the reaction chamber is set at approximately 30 mTorr. No gas source heating may be necessary if the vapor pressure is sufficient. The distance between the two CCP electrodes is kept at 1.35 cm and the top electrode RF power is fixed at 750 W. The bottom electrode RF power is varied to analyze the performance of the molecule. The reaction chamber contains a substrate having silicon-containing films thereon, similar to those shown in FIG. 1a . The antireflective coating layer 108 is patterned/etched by a fluorocarbon (e.g., CF4 and CH2F2) and oxygen-containing gas (e.g., O2). The amorphous carbon mask layer is patterned/etched by an oxygen-containing gas. The SiO and SiN layers 104 are patterned by the plasma of the disclosed iodine-containing etching compounds (e.g., C4F9I) and Argon. Argon is independently introduced into the chamber at a 250 sccm flow rate. C4F9I is independently introduced into the chamber at 15 sccm. O2 is independently introduced into the chamber and varied from 0 sccm to 20 sccm to determine optimum etching conditions. An aperture having an aspect ratio equal to or greater than 10:1 is produced, which may be used as a channel hole or contact hole or staircase etch, slit etch in 3D NAND. Similar example may be used for other stack layers as shown in FIGS. 2 and 3 a.
  • In another non-limiting exemplary plasma etch process, C4F9I is introduced into a 200 mm Dual CCP plasma etch tool using a controlled gas flow device. The controlled gas flow device may be a mass flow controller. In case of high boiling point molecules, a special low pressure drop mass flow controller from Brooks Automation (No. GF120XSD), MKS Instruments, etc., may be used. The pressure of the reaction chamber is set at approximately 30 mTorr. No gas source heating may be necessary if the vapor pressure is sufficient. The distance between the two CCP electrodes is kept at 1.35 cm and the top electrode RF power is fixed at 750 W. The bottom electrode RF power is varied to analyze the performance of C4F9I. The reaction chamber contains a substrate 100 having a thick SiO layer 104 a thereon, similar to the layer shown in FIG. 2. Prior to this process, the antireflective coating layer 108 is removed by a fluorocarbon (e.g., CF4) and oxygen-containing gas (e.g., O2) and the A-c mask layer 106 is removed by an oxygen-containing gas. Argon is independently introduced into the chamber at a 250 sccm flow rate. C4F9I is independently introduced into the chamber at 15 sccm. 02 is independently introduced into the chamber at 0-20 sccm to determine optimum etching conditions. An aperture having an aspect ratio equal to or greater than 10:1 is produced, which may be used as a contact hole in DRAM. Similar examples may be used for other stack layers as shown in FIGS. 1a and 3 a.
  • The silicon-containing films and the activated iodine-containing etching gas react to form volatile by-products that are removed from the reaction chamber. The a-C mask, antireflective coating, and photoresist layer are less reactive with the activated etching gas. Thus, the activated etching gas selectively reacts with the silicon-containing films to form volatile by-products.
  • The temperature and the pressure within the reaction chamber are held at conditions suitable for the silicon-containing film to react with the activated etching gas. For instance, the pressure in the chamber may be held between approximately 0.1 mTorr and approximately 1000 Torr, preferably between approximately 1 mTorr and approximately 10 Torr, more preferably between approximately 10 mTorr and approximately 1 Torr, and more preferably between approximately 10 mTorr and approximately 100 mTorr, as required by the etching parameters. Likewise, the substrate temperature in the chamber may range between about approximately −196° C. to approximately 500° C., preferably between approximately −120° C. to approximately 300° C., more preferably between approximately −100° C. to approximately 50° C.; and more preferably between approximately −10° C. to approximately 40° C. Chamber wall temperatures may range from approximately −196° C. to approximately 300° C. depending on the process requirements.
  • The reactions between the silicon-containing film and the activated etching gas result in anisotropic removal of the silicon-containing films from the substrate. Atoms of nitrogen, oxygen, and/or carbon may also be present in the silicon-containing film. The removal is due to a physical sputtering of silicon-containing film from plasma ions (accelerated by the plasma) and/or by chemical reaction of plasma species to convert Si to volatile species, such as SiFx, wherein x ranges from 1-4.
  • The plasma activated vapor of the disclosed iodine-containing etching compounds preferably exhibits high selectivity toward the mask and etches through the alternating layers of SiO and SiN resulting in a vertical etch profile with no bowing or roughness, which is important for 3D NAND applications. Additionally, plasma activated vapor deposits polymer on sidewall to minimize feature profile deformation. For other applications, such as DRAM and 2D NAND, for example, the plasma activated etching gas under different process conditions may selectively etch SiO from SiN. The plasma activated etching gas may selectively etch SiO and/or SiN from mask layers, such as a-C, photoresist, p-Si, or silicon carbide; or from metal contact layers, such as Cu, W, Ru, etc.; or from channel regions consisting of SiGe or polysilicon regions.
  • The disclosed etch processes using the disclosed iodine-containing etching compounds as the etching gases produce channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, contact etch, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films. The resulting aperture may have an aspect ratio ranging from approximately 10:1 to approximately 200:1 and a diameter ranging from approximately 5 nm to approximately 500 nm, preferably less than 100 nm. For example, one of ordinary skill in the art will recognize that a channel hole etch produces apertures in the silicon-containing films having an aspect ratio greater than 50:1.
  • Typical materials that need to be etched may be SiO. A process of etching SiO may be relevant to etching trenches in Borophosphosilicateglass (BPSG), Tetraethylorthosilicate (TEOS), or low deposition rate TEOS (LDTEOS). An etch stop layer may be silicon nitride or silicon oxygen nitride (SiON) or poly silicon. A mask material used may be a-C, p-Si, or photo resist materials. Herein, the disclosed iodine-containing etching compounds are applied to etch SiO, SiN, p-Si and/or a-C substrate films.
  • As shown in the examples that follow, evaluations of dry etching of SiO, SiN, p-Si and a-C films with the disclosed iodine-containing etching compounds show that the iodine-containing HFCs yield highest selectivity of silicon oxide to amorphous carbon, silicon nitride and p-Si than the prior art fluorocarbons. The reason for high selectivity may be attributed to the formation of low F/C iodine containing fragments during plasma dissociation of the etch gases, which results in the formation of a protective polymer film on the substrates. Additionally, the iodine is ionized and bombards the surface with the heavy I ion similar to inert gases such as Ar, Kr, and Xe. Also the iodine ionized atoms modifies the surface of the organic hard mask, by doping it and improving its etch resistance, so as to favor high aspect ratio etch. The activated iodine-containing etching compound produces iodine ions, which strengthens the patterned mask layer, thereby reinforcing and minimizing damage to a patterned mask layer while forming a patterned structure in the substrate. The etching gas results presented herein show they are not only ready for patterned structure etch process, such as contact etch process, but also may be beneficial for other etching processes on silicon or metal containing substrates, including low k etching processes. In addition, in the process of forming the patterned structure by etching with the disclosed iodine-containing etching compound, an etch resistance of the pattern mask layer may be increased by doping iodine to the surface of the pattern mask layer, thereby modifying the surface. In this case, the iodine ions from the activated iodine-containing etching compound are implanted into the patterned mask layer (i.e., the surface and/or the body/bulk of the patterned mask layer) while etching the silicon-containing film from the substrate to form the patterned structure. Besides, the disclosed iodine-containing etching compounds are suitable for reduction of the global warming potential caused by perfluorocarbon compounds.
    • EXAMPLES
  • The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.
  • In the following examples, experiments were carried out with commercial LAM tool 4520XLe 200 mm (CCP dual frequency plasma) or alternatively with commercial AMEC 300 mm Primo SSC HD-RIE etcher. Planar wafers were purchased from Advantive Tech. Planar wafers tested are four different substrates below.
  • 2 μm PECVD TEOS (SiO) on Si substrate;
  • 2 μm PECVD Si3N4 (SiN) on Si substrate;
  • 300 nm LPCVD polysilicon (poly-Si) on Si substrate; and
  • 350 PECVD amorphous carbon (a-C) on Si substrate.
  • For planar tests, etch rate (ER) were measured using an Ellipsometer and/or scanning electron microscope (SEM) by measuring the change in etch thickness as a function of etching time. The etching experiment were performed on four 1.5×1.5 cm2 coupons having four different substrate materials including SiO, SiN, p-Si and a-C, listed above. The coupons are placed on 200 mm diameter carrier wafer and held in contact by using silicon oil or thermal paste. Alternatively, double sided carbon tape obtained from 2 spi manufacturer may have been used to stick coupons on carrier wafer.
  • Etching tests were performed at a pressure of 30 mTorr, source power of 750 W (27 MHz), bias power of 1500 W (2 MHz), and temperature 20° C. The feed mixture contains 250 sccm of Ar, 15 sccm of etch gas, while 02 is varied in the range 0 to 20 sccm.
  • To prove the repeatability, each etching test have been repeated at least three times. Standard deviation of the average of the three measurements is shown as error bar in the chart. Subsequently, polymer composition was studied by X-Ray Photoelectron Spectroscopy (XPS).
    • COMPARATIVE EXAMPLE
  • FIG. 4 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C3F7I (CAS No. 754-34-7), O2 and Ar. In FIG. 4, the y-axis represents etch rates; the x-axis is O2 flow rate in sccm; the 1-C3F7I flow rate is fixed at 15 sccm, the Ar is fixed at 250 sccm while the O2 flow rate is varied from 0 to 20 sccm. As the O2 flow rate raise from 0 to 20 an inversely proportional trend is observed: SiO2 ER decreases as O2 flow rate increase, while SiN, p-Si and a-C ERs increase as O2 flow rate increases. Thus the highest selectivity, meaning the ratio between SiO ER and other materials ER rate is shown when no oxygen is flown. At 0 sccm of O2, SiO2/a-C selectivity is 38.5, SiO2/p-Si selectivity is 22, and SiO2/SiN selectivity is 11.
  • FIG. 5 is a graph demonstrating the electron impact ionization energy (eV) versus species concentration (Torr) of C3F7I. The dominant fragments produced at between 10 and 20 eV are CF3, C3F7, and I.
    • Example 1
  • FIG. 6 is a graph demonstrating etch rates of SiO, SiN, p-Si and a-C with 1-C4F9I, O2 and Ar. In FIG. 6, the y-axis represents etch rates; the x-axis is O2 flow rate in sccm; the 1-C4F9I flow rate is fixed at 15 sccm, the Ar is fixed at 250 sccm while the O2 flow rate is varied from 0 to 20 sccm.
  • As the O2 flow rate raise from 0 to 20 an inversely proportional trend is observed: SiO2 ER decreases as O2 flow rate increases, while SiN, p-Si and a-C ERs increase as O2 flow rate increases. Thus the highest selectivity, meaning the ratio between SiO ER and other materials ER rate is shown when no oxygen is flown. At 0 sccm of O2, SiO2/a-C selectivity is 71, SiO2/p-Si selectivity is 47, and SiO2/SiN selectivity is 17. Comparing to the results of 1-C3F7I shown in FIG. 4, 1-C4F9I is better than 1-C3F7I both in terms of SiO2 ER and selectivity of SiO2 vs all the other materials tested.
  • Addition of iodine gives increased fragmentation for both 1-C3F7I and 1-C4F9I due to the C—I weaker bond. The lower ionization threshold of the Iodine ion bombarding the surface yields increased selectivity for etching oxide (SiO) versus a-C, poly-Si or SiN. Table 3 is a comparison with benchmark standard etch gases cC4F8 and C4F6, commonly used in the industry. 1-C4F9I shows higher SiO2/a-C selectivity than benchmark gases (cC4F8 and C4F6), respectively ˜88% and 85% higher, and ˜46% higher than 1-C3F7I. 1-C4F9I shows higher SiO2 ER than benchmark gases (cC4F8 and C4F6), respectively 8.6% and 16.4% higher, and 9% higher than 1-C3F7I. FIG. 10 and FIG. 11 are graphs demonstrating etch rates of SiO, SiN, p-Si and a-C with cC4F8 and C4F6, respectively.
  • TABLE 3
    SiO2 ER [nm/min] SiCO2/a-C selectivity
    cC4F8 585 8.7
    C4F6 535 10.7
    1-C3F7I 580 38.5
    1-C4F9I 640 71
    • Example 2
  • XPS data analysis after 1-C4F9I etching on different a-C mask layers with or without dopants.
  • XPS angle resolved at 75° sample tilting and depth profile were performed to analyze the polymer composition on a-C masks and benchmarked with SiO2 substrate.
  • In order to simulate the polymer layer formation occurring on the top surface and on the sidewall during plasma processing etch of patterns the process condition were tuned: a-C mask, Boron-doped a-C [a-C(B)] and Tungsten-doped a-C [a-C(W)] and SiO2 (TEOS) coupons were etched at 30 mTorr for 60 sec, source power 750 W (27 MHz), and bias power 1500 W (2 MHz) at the substrate. The process feed the mixture contains 125 sccm of Ar, 30 sccm of 1-C4F9I and no O2. The neutrals and the active species reaching the surface stick to the surface, based on their sticking coefficient, and deposit a thin polymer layer. This thin polymer layer may be responsible for sidewall passivation and often provides the selectivity. Table 4 to Table 6 are XPS angle resolved at 75° on different a-C layers after 1-C4F9I etching.
  • TABLE 4
    XPS angle resolved at 75° on a-C
    BE Atomic conc. Error Mass conc. Error
    [eV] [%] [%] [%] [%]
    O 1s 529.90 4.94 0.19 4.57 0.17
    I 3d 617.50 2.07 0.03 15.22 0.21
    F 1s 684.30 38.65 0.32 42.47 0.30
    C 1s 282.30 54.34 0.35 37.75 0.32
  • TABLE 5
    XPS angle resolved at 75° on a-C(B)
    BE Atomic conc. Error Mass conc. Error
    [eV] [%] [%] [%] [%]
    O 1s 529.40 4.57 0.18 4.26 0.16
    I 3d 616.60 2.09 0.03 15.44 0.21
    F 1s 683.50 37.38 0.38 41.38 0.33
    C 1s 282.30 52.55 0.47 36.77 0.35
    B 1s 184.00 3.41 0.57 2.15 0.36
  • TABLE 6
    XPS angle resolved at 75° on a-C(W)
    BE Atomic conc. Error Mass conc. Error
    [eV] [%] [%] [%] [%]
    O 1s 530.60 6.05 0.26 5.55 0.24
    I 3d 617.80 1.84 0.04 13.39 0.27
    F 1s 684.70 34.33 0.40 37.41 0.38
    C 1s 282.80 57.39 0.45 39.53 0.42
    W 4f 31.70 0.39 0.02 4.12 0.19
  • Superficial atomic concentration of Iodine in the 3 different a-C masks [a-C, a-C(B) and a-C(W)] is comparable: ˜2%.
  • For XPS depth profile, large cluster ion gas Ar1000 + at 5 keV ion energy have been used, instead of monoatomic Ar+ in order to minimize the chemical damage and avoid potential knock-on of iodine atoms during Argon sputtering, which is likely to happen during organic material sputtering, such as fluorocarbon polymer or amorphous carbon.
  • Depth profile on a-C substrate: Superficial atomic concentration (%) is listed in Table 7 and FIG. 7. Depth profile on a-C(B) substrate: Superficial atomic concentration (%) is listed in Table 8 and FIG. 8. Depth profile on a-C(W) substrate: Superficial atomic concentration (%) is listed in Table 9 and FIG. 9. Superficial atomic concentration after 1-C4F9I etch on SiO2 substrate is listed in Table 10.
  • TABLE 7
    C1s F1s O1s I3d
    64.4 22.6 10.0 1.5
  • TABLE 8
    C1s F1s O1s B 1s I3d
    62.0 20.5 10.7 4.0 1.6
  • TABLE 9
    C1s F1s O1s W 4f I3d
    62.5 23.0 10.4 0.9 1.8
  • TABLE 10
    Si 2p C1s F1s O1s I3d
    24.0 18.4 11.6 53.1 0.3
  • The disclosed Iodine-containing etching compound show an interesting behavior during a-C mask etch compared to etch of Si-based materials. According to XPS data, Iodine penetrates deeply on a-C mask, similar to a doping effect, helping preserving it during etch.
      • Iodine detected in all a-C, a-C(B) and a-C(W) around 2% superficially and in lower amount deeper in the bulk;
      • Superficial CxFyIz (x≤4, y≤9, z≤1) polymer detected on all a-C masks (up to 50 sec etch);
      • Iodine vs Fluorine penetration in the different a-C masks:
        • In a-C: I penetrates deeper than F (410 vs 450 sec respectively),
        • In a-C(W): I penetrates deeper than F (90 vs 45 sec respectively),
        • In a-C(B): F penetrates deeper than I (210 vs 90 sec respectively);
      • In comparison Iodine almost not detected (0.3%) on SiO2 substrate, very thin FC polymer formed only.
  • This example shows that Iodine ions modify the surface of the pattern mask by depositing a polymer layer composed of CxFyIz atoms as well as the iodine ions penetrate deep into the bulk of the pattern mask layer. Correlating the XPS data regarding the composition of pattern mask after etching with the etching data shown in the Example 1, the effect of iodine ions can be observed. The iodine-containing etching compounds help preserving the pattern mask layer by increasing the crosslinking with the organic layer, making the pattern mask stronger and increasing its etch resistance.
  • Although the subject matter described herein may be described in the context of illustrative implementations to process one or more computing application features/operations for a computing application having user-interactive components the subject matter is not limited to these particular embodiments. Rather, the techniques described herein may be applied to any suitable type of user-interactive component execution management methods, systems, platforms, and/or apparatus.
  • It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.
  • While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.

Claims (20)

1. A method for forming a patterned structure, the method comprising the steps of:
introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and a patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4;
activating a plasma to produce an activated iodine-containing etching compound; and
allowing an etching reaction to proceed between the activated iodine-containing etching compound and the silicon-containing film to selectively etch the silicon-containing film from the patterned mask layer, thereby forming the patterned structure.
2. The method of claim 1, further comprising the step of introducing an oxidizer into the reaction chamber, wherein the oxidizer is selected from O2, O3, CO, CO2, NO, N2O, NO2, H2O, H2O2, COS, SO2 and combinations thereof.
3. The method of claim 1, further comprising the step of introducing an inert gas into the reaction chamber, wherein the inert gas is selected from the group consisting of He, Ar, Xe, Kr, Ne and N2.
4. The method of claim 1, wherein the iodine-containing etching compound is C4F9I or its isomers.
5. The method of claim 1, wherein the silicon-containing film comprises a layer of silicon oxide (SiO), silicon nitride (SiN), crystalline Si, poly-silicon (p-Si), polycrystalline silicon, amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON and SiaObHcCdNe, where a>0; b, c, d and e≥0, alternating SiO and SiN (ONON) layers, alternating SiO and p-Si (OPOP) layers.
6. The method of claim 5, wherein the silicon-containing film optionally contains dopants such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge, and combinations thereof.
7. The method of claim 5, wherein an etch rate of etching the silicon oxide layer using the iodine-containing etching compound is higher than an etch rate of etching the silicon oxide layer using as an alternative etching gases cC4F8, C4F6, CF4, CH3F, CF3H, CH2F2, and combinations thereof.
8. The method of claim 5, wherein the iodine-containing etching compound plasma etches the alternating SiO and SiN (ONON) layers having a selectivity between approximately 1:2 to approximately 2:1 with respect to the SiO layer versus SiN layer.
9. The method of claim 5, wherein the iodine-containing etching compound plasma etches the alternating SiO and SiN (ONON) layers having a selectivity of approximately 1:1 with respect to the SiO layer versus SiN layer.
10. The method of claim 5, wherein the iodine-containing etching compound plasma etches the alternating SiO and p-Si (OPOP) layers having a selectivity between approximately 1:2 to approximately 2:1 with respect to the SiO layer versus p-Si layer.
11. The method of claim 5, wherein the iodine-containing etching compound plasma etches the alternating SiO and p-Si (OPOP) layers having a selectivity of approximately 1:1 with respect to the SiO layer versus p-Si layer.
12. The method of claim 1, wherein the patterned mask layer is an amorphous carbon layer, a doped amorphous carbon layer, a photoresist layer, an anti-reflective layer, an organic planarization layer, and combinations thereof.
13. The method of claim 1, wherein the activated iodine-containing etching compound selectively etches the silicon-containing film from a landing layer located at the bottom of the silicon-containing film to be etched.
14. The method of claim 13, wherein the landing layer is a metal layer selected from W, Cu, Al, Ru, Pt, Ti, Ta, Ni, Co, Mo, Mn, Nb, Cr, Rh, Pd, Ir, V, Au, Ag or combinations thereof.
15. The method of claim 13, wherein the landing layer is a metal oxide layer or a metal nitride layer selected from AlO, WO, HfO, TiO, TaO, InO, WO, CrO, RuO, CoO, MoO, ZrO, SnO, TiN, TaN, HfN, AlN, WN, MoN, NiN, NbN, CrN, RuN, CoN, ZrN, SrN or combinations thereof.
16. The method of claim 1, wherein the patterned structure formed in the silicon-containing film has an aspect ratio between approximately 1:1 and approximately 200:1.
17. A method of reinforcing and/or strengthening and/or minimizing damage of a patterned mask layer while forming a patterned structure in a substrate, the method comprising:
introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and the patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4; and
etching the silicon-containing film from the patterned mask layer to form the patterned structure using an activated iodine-containing etching compound formed by activating a plasma,
wherein the activated iodine-containing etching compound produces iodine ions, which are implanted into the patterned hardmask layer, thereby strengthening the patterned mask layer.
18. The method of claim 17, wherein the iodine-containing etching compound is C4F9I or its isomers.
19. A method of increasing etch resistance of a patterned mask layer in a process of forming a patterned structure in a substrate, the method comprising:
introducing a vapor of an iodine-containing etching compound into a reaction chamber containing a substrate having a silicon-containing film disposed thereon and the patterned mask layer disposed on the silicon-containing layer, wherein the iodine-containing etching compound has the formula CnHxFyIz, wherein 4≤n≤10, 0≤x≤21, 0≤y≤21, and 1≤z≤4;
activating a plasma to produce an activated iodine-containing etching compound capable of doping iodine into the patterned mask layer; and
implanting iodine ions from the activated iodine-containing etching compound into the patterned mask layer while etching the silicon-containing film from the patterned mask layer to form the patterned structure,
thereby modifying the patterned mask layer with iodine to increase the etch resistance of the patterned mask layer.
20. The method of claim 19, wherein the iodine-containing etching compound is C4F9I or its isomers.
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